Connecting a 3.5" serial port
ZXNet echo conference «hardware.zx»
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* Forwarded by Kirill Frolov (500:812/1.507)
* Area : NETMAIL (My soap)
* From : Kirill Frolov, 2:5030/827.2 (27 Nov 02 22:11)
*To: Yuri Potapov
* Subj : 3.5" drive connection
================================================================================
Press RESET immediately, Yuri!
26 Nov 02 21:11, Yuri Potapov wrote to Kirill Frolov:
YP> in this case I have this idea
YP> on one side there is a green ZS Scorpion, there is no confusion
YP> on the other hand, not a very sophisticated PC running Linux
YP> most likely, the PC will have a CD, 1.44 drive, screw, modem
YP> but in general it should act as a server from/where I will download
YP> files
YP> modem emulation is not needed
YP> much of what I will transmit should go as commands
YP>console
YP> the spec will have to play the role of a client, including how I do
YP> explained that it is possible to surf the Internet via Linux using
YP> regular terminal
That is, you need either a network (telnet, ssh...), which does not exist, or a connectionvia serial port (Spectrum terminal emulation). Usually remote
control of a machine via a unix terminal is only possible via a network or
serial interface (modem).
YP> and this will already be more promising than trying to write in Spec now
YP> browser and tcp/ip and so on
Well, it’s for such purposes, IMHO, that you need to write. Only with a view to
using the resources of a pussy that is not in the next room, but accessible
via the Internet. For example, try telneting cyberspace.org - you can get
account on a machine running SunOS and use it to access other
network information resources.
There is no network on the Spectrum yet, well, at least there is definitely no telnet there.
Therefore, there are two options left for you: ZX <- serial interface -> PC.
The role of a “serial interface” can be either a cable or a pair
modems.
If you already have an ISA modem installed on your Spectrum, then just connect
you will receive a multicard from the PC and you will receive a serial port. If you need
parallel and modem, or do you need several serial ports then
you will have to think about upgrading the modem connection circuit. If the modem is on
Spectrum is not available, that is, there are 2 options: through a multicard (for example, by
Kondratiev scheme) and through software emulation of asynchronousSpectrum serial interface. In case of software emulation it is not necessary
The piss multicard is already in short supply.
The "minimal" null modem cable for connecting two computers contains
just three wires:
ZX PC
----------------- -----------------
signal DB9S DB25S signal DB9S DB25S
TD 3 2 <----------> RD 2 3
RD 2 3 <-----------> TD 3 2
GROUND 5 7 <-----------> GROUND 5 7
Columns DB9S and DB25S indicate the pin numbers on the corresponding
connectors.
There are several standard connectors for this interface, and most
popular ones are DB9S and DB25S (the letter S means Socket, that is, a socket. This
connectors with “holes” on the cable and with “pins” on the computer). In modern
IBM PC computers usually use DB9.
The minimum cable version has some disadvantages, in particular it
provides only software flow control, which is completely unsuitable for
use in the case of software emulation of a serial interface on
Spectrum (Spectrum can only receive data in a port polling cycle, but when
in the absence of other signal wires, he cannot in any way communicate to another
whether the computer is ready to receive it or not). In case of hardware implementationinterface on the Spectrum, the use of a 3-wire cable is also undesirable,
since it is difficult for Spectrum with its slowness to guarantee timely
extracting received data from the receiver buffer. Mentioned disadvantage
There is no 3-wire cable in the 4-wire or 5-wire interface, where
hardware flow control is used:
ZX PC
----------------- -----------------
signal DB9S DB25S signal DB9S DB25S
TD 3 2 <----------> RD 2 3
RD 2 3 <-----------> TD 3 2
RTS 7 4 <-----------> CTS 8 5
* CTS 8 5 <--(*)------> * RTS 7 4
GROUND 5 7 <-----------> GROUND 5 7
The signal marked with an asterisk '*' in the case of a 4-wire interface may not be
be used, but its non-use is undesirable: this signal provides
protection against overflow of the receiver buffer in the PC, just like a signal does
RTS for Spectrum.
5-wire interface provides a complete full-duplex transmission channel
information with hardware flow control. But if it is necessary to transmit
some control information outside the transmission channel, for example
ready/unready, reset/handshake, as often used in
modems, then you need a full-fledged interface consisting of 9 wires:ZX PC
----------------- -----------------
signal DB9S DB25S signal DB9S DB25S
TD 3 2 <----------> RD 2 3
RD 2 3 <-----------> TD 3 2
RTS 7 4 <-----------> CTS 8 5
CTS 8 5 <-----------> RTS 7 4
DTR 4 20 <--------+--> DSR 6 6
DSR 6 6 <--+-----)--> DTR 4 20
* DCD 1 8 <--+ +--> DCD 1 8
* RI 9 22 RI 9 22
GROUND 5 7 <-----------> GROUND 5 7
Signals marked with asterisks ('*') RI and DCD are used only in modems.
RI is an input at the terminal (computer) indicating the arrival of a call, DCD
signals the establishment of communication (presence of carrier). In this case, RI is not
is used, and the DCD is connected to the DTR signal from the remote side, which
provides "carrier appearance" when signaling the readiness of the remote side.
This was the wiring of a full-fledged null modem cable. She doesn't
coincides with the wiring of a regular modem cable!
In your case, I would use a 5-wire interface. As
cable, if it is impossible to get it ready-made, it is better to take a modem cable and
make a special adapter. I do not recommend making a cable
yourself, it’s better to take a ready-made one.In a modem cable, all signals are connected one to one, and in a null modem
reception and transmission signals, RTS-CTS, DTR-DSR are swapped. Below is
complete pinout of the serial interface. There are several standards
here we mean the RS-232C interface, used in most
personal computers.
Designation Connector contact Direction
RS232 DB9 DB25 output
PG - 1 - protective ground
(protect ground)
TD 3 2 output data transmission
(transmit data)
RD 2 3 input data reception
(receive data)
RTS 7 4 output request transfer
(request to send) data
CTS 8 5 input ready for
(clear to send) data reception
DSR 6 6 input ready
(data set ready) devices
data transmission
SG 5 7 - signal
(signal ground) common wire
DCD 1 8 input detection
(data carrier detected) carrier
DTR 4 20 output ready
(data terminal ready) terminalRI 9 22 input bell
(ring indicator)
Historically, although it no longer makes much sense,
that all devices using the RS-232C interface are divided into 2 types: devices
data transmission (DCE == Data Connection Equipment, e.g. modems) and final
equipment, terminals (DTE == Data Terminal Equipment, for example, when
When connecting a modem to a computer, the computer plays the role of a terminal). In fact
both devices are equivalent, but from this division they are designated differently
signals: DTR or DSR, RTS or CTS... and there is a little confusion. So here it is
the above table refers to DTE devices, that is, terminals
(computers). The pin numbers for DTE devices are correct, but for DCE
devices (modems) must be swapped TD and RD, CTS and RTS, DSR and DTR.
Hence, by the way, the difference between “straight” modem cables and “twisted” ones
null modem. And besides, in the table above there are only
signals used in the IBM-PC and most other computers. Full version
interface defines a larger number of signals on the DB25 connector.
When connecting an ISA multicard from an IBM-PC computer, problems may arise.
problems with connecting the remote connector cable ("miscarriage") to the multicard.
The fact is that there are several different options for pinout of contacts onmultimap. Here are the main ones:
Contact on the multicard Contact on the connector
Var.1 Var.2 Var.3 Var.4 DB9 DB25
(10) (10) (10) 1 - 1
3 5 3 3 3 2
2 3 4 5 2 3
7 4 8 7 7 4
8 6 7 9 8 5
6 2 9 11 6 6
5 9 1 13 5 7
1 1 5 15 1 8
4 7 2 14 4 20
9 8 6 18 9 22
Version 1 8-bit multicard loop
Ver.2 loop of 16-bit multicards
Version 3 cable for ports integrated on the motherboard
Version 4 wide cable to 25-pin connector
From everything written about how a multicard is connected, for example, by
Kondratiev's scheme should already be clear. Naturally, the ISA slot should
3 voltages are supplied: -12 volts, +12 volts, and +5 volts. Herself
The Kondratiev diagram for connecting an ISA modem (multi-card) to the Spectrum is here:
Original Kondratieff adapter circuit for connection
internal modem.
DD1
__ +---+
RD -----------------+1 | _____
| +------- IORD# (modem)
+---+ |
DD1 | +---+
+---+ |
A4 ----+1 | |
____ | +----+
IORQ --+ | |
+---+ | DD1 | +---+
+---+1 | _____
__ | +---+-- IOWR# (modem)
WR -----------------+ | |
+---+ |
|
+--------------------+
|
| DD2
| +--------+
+5v - | ---o R |
| | Q +-----+
+----/ C | |
| | |
A11 --------> D _ | |
_____ | Q O-- |
RESET --+---o S | |
| +--------+ |
| |
| DD3 |
| +---+ |
| |1 | |
+----+ O--------------- RESET (modem)
| | |
+---+ |
|
|
|
| DD1
DD3 | +---+
+---+ +--+1 | ---
|1 | | +------ NMI
(modem) IRQ4 ----+ O---------+ |
| | +---+
+---+
A8 ------------------- A0 (modem)
A9 ------------------- A1 (modem)
A10 ------------------- A2 (modem)
D0..D7 ---------------- D0..D7 (modem)
+5v -------------------- A3..A10 (modem)
GND -------------------- AEN (modem)
List of elements:
DD1 1533LL1
DD2 1533TM2
DD3 1533ЛH1
Signals marked in brackets "(modem)" are connected to
corresponding pins of the ISA slot for the modem, the rest
the signals are connected directly to the computer bus.
Accessing modem registers via ports
The modem registers are accessible through the microprocessor I/O ports.
The address is calculated like this:
0xF0EF + (0x0800 if NMI interrupts are disabled) + (register_address*0x100)
The interrupt enable trigger from the modem switches only when
output to the modem ports.
NOTE: Instead of non-maskable (NMI), you can use maskable
(INT) interrupt. Not all programs support this yet, but THIS IS MORE
CORRECT DECISION. THE USE OF NMI CAN POTENTIALLY RESULT IN
STACK OVERFLOW AND DISRUPTION OF NORMAL OPERATION OF PROGRAMS.
Just in case, I’m also bringing a modified one (so that it doesn’t work with the 7FFD port).
conflicted) Shepelev’s scheme:
Modified Shepelevsky scheme, supported in the Melon program.
D0..D7 ----------------------- D0..D7 (modem)
A8 -------------------------- A0 (modem)
A9 -------------------------- A1 (modem)
A10 -------------------------- A2 (modem)
A11 -------------------------- A3 (modem)
A12 -------------------------- A8 (modem)
A13 -------------------------- A9 (modem)+5v ---------------------- A4 (modem)
+5v ---------------------- A5 (modem)
GND ----------------------- AEN (modem)
+---+
A14 --------+ 1 |
| +---+
A15 --------+ | |
+---+ |
DD1.1 | +---+
+--+ 1 |
| o----+---- A7 (modem)
A6 ---------------------+ | |
+---+ +---- A6 (modem)
DD2.1
____ +---+
IORQ ----+---+ 1 |
__ | | +----------- IORD# (modem)
RD -----(---+ |
| +---+
| DD1.2
| +---+
+---+ 1 |
__ | +----------- IOWR# (modem)
WR ---------+ |
+---+
DD1.3
+---+
GND -----+ 1 |
_____ | o----------RESET (modem)
RESET -------+ |
+---+
DD2.2
Read more:
DD1 1533ЛЛ1
DD2 1533ЛЕ1
Read the story of the story
The story of the story of the story of the story микропроцессора,
Read more about the article:
0x38BF + адрес_регистра_модема
In the end the story was written. использование прерыванийfrom the modem, but this feature can be added by connecting one of the outputs
modem interrupts via an inverter with an "open collector" output
(chip 555ЛH2) with an INT signal (maskable interrupt) on the bus
ZX-Spectrum. An NPN bipolar transistor can act as an inertor
(for example KT315) in the corresponding connection circuit.
The above schemes have some disadvantages. For example, they
most likely will not work if you connect the modem and
computer with long (>10cm) wires. The whole problem here is
excessive inductance of conductors. If the modem does not work, you can
try passing signals A8,A9,A10,IOWR and IORD through the trigger
Schmidt installed in close proximity to the ISA slot or through
resistors with a resistance of 30-50 ohms.
Pin assignments of the short (8-bit) ISA slot:
+---------+---------------+-----------------+---------+
| contact | signal | signal | contact |
+-+-----+-+---------------+-----------------+-+-----+-+
| A1 | IOCHK | GND | B1 |
+-----+-----------------+-------------------+-----+
| A2 | D7 | RESET | B2 |
+-----+-----------------+-------------------+-----+
| A3 | D6 | +5v | B3 |
+-----+-----------------+-------------------+-----+
| A4 | D5 | IRQ2/9 (*) | B4 | +-----+-----------------+-------------------+-----+
| A5 | D4 | -5v | B5 |
+-----+-----------------+-------------------+-----+
| A6 | D3 | DRQ2 | B6 |
+-----+-----------------+-------------------+-----+
| A7 | D2 | -12v | B7 |
+-----+-----------------+-------------------+-----+
| A8 | D1 | OWS2# | B8 |
+-----+-----------------+-------------------+-----+
| A9 | D0 | +12v | B9 |
+-----+-----------------+-------------------+-----+
| A10 | IOCHDRY | GND | B10 |
+-----+-----------------+-------------------+-----+
| A11 | AEN | SmemWR# | B11 |
+-----+-----------------+-------------------+-----+
| A12 | A19 | SmemRD# | B12 |
+-----+-----------------+-------------------+-----+
| A13 | A18 | IOWR# | B13 |
+-----+-----------------+-------------------+-----+
| A14 | A17 | IORD# | B14 |
+-----+-----------------+-------------------+-----+
| A15 | A16 | DACK3# | B15 |
+-----+-----------------+-------------------+-----+
| A16 | A15 | DRQ3 | B16 |
+-----+-----------------+-------------------+-----+
| A17 | A14 | DACK1# | B17 |
+-----+-----------------+-------------------+-----+
| A18 | A13 | DRQ1 | B18 |
+-----+-----------------+-------------------+-----+
| A19 | A12 | REFR# | B19 |
+-----+-----------------+-------------------+-----+
| A20 | A11 | BClock | B20 |
+-----+-----------------+-------------------+-----+
| A21 | A10 | IRQ7 | B21 |
+-----+-----------------+-------------------+-----+
| A22 | A9 | IRQ6 | B22 |
+-----+-----------------+-------------------+-----+
| A23 | A8 | IRQ5 | B23 |
+-----+-----------------+-------------------+-----+
| A24 | A7 | IRQ4 | B24 |
+-----+-----------------+-------------------+-----+
| A25 | A6 | IRQ3 | B25 |
+-----+-----------------+-------------------+-----+
| A26 | A5 | DACK2# | B26 |
+-----+-----------------+-------------------+-----+
| A27 | A4 | TC | B27 |
+-----+-----------------+-------------------+-----+
| A28 | A3 | BALE | B28 |
+-----+-----------------+-------------------+-----+
| A29 | A2 | +5v | B29 |
+-----+-----------------+-------------------+-----+
| A30 | A1 | OSC | B30 |
+-----+-----------------+-------------------+-----+
| A31 | A0 | GND | B31 |
+-----+-----------------+-------------------+-----+
Note: some modem (multi-card) models are designed
to connect to long (16-bit)
ISA slot. You can connect them without any problems
and into a short slot when used
interrupts in the range IRQ1..IRQ7.
NOTE: Instead of the Non-Maskable Interrupt (NMI) used in
Kondratiev circuit, you can use a maskable (INT) interrupt. Not yet
all programs support this, but THIS IS A MORE CORRECT SOLUTION. USE
NMI CAN POTENTIALLY RESULT IN A STACK OVERFLOW AND INTERRUPTION OF NORMAL
PROGRAM OPERATIONS.
Everything should be clear by now with connecting ISA multicards and modems. Remaining
two more options: a serial port based on i8251 (K580VV51) - if necessary
I’ll find a diagram, but there’s a lot of soldering required, and the speed is only 9600. And another option is this
software emulation of a serial interface. Everything is here in terms of soldering
much simpler, you need two software-controlled ports (you need two binary
discharge) on the output and two ports on the input. If you plan to useinterface without flow control, you can get by with one output port and one
at the entrance. But this is a very unreliable solution; it requires the use of special
data transfer protocols that guarantee error-free data transfer. Yes
Another option is using flow control only in the direction from PC to ZX
(see above, 4-wire interface), but it’s still better to use a full-fledged
5-wire interface. Let's say we already have two output ports, two ports
at the entrance. The ports are based on TTL logic, that is, they transmit binary signals with
levels from 0 to +5 volts. They must be coordinated with the RS-232C interface. Below
there is a table explaining the coding of signals in TTL logic and interface
RS-232C:
Signal TTL logic RS-232C
-----------------------------------
log. 0. 0..1.5 volts +3..12 volts
log. 1. 2..5 volts -3..-12 volts
Coordination is best accomplished using specially designed
this microcircuit (imported): receiver - 1489, transmitter - 1488. There are
and Soviet analogues of these microcircuits, but I don’t remember their designations. There is also
newer and easier-to-use microcircuits that allow TTL matching
logic with RS-232C interface, for example MAX-232. Convenience lies in
no need to have a power source with a voltage of -12 and +12 volts(generated inside the microcircuit, on capacitors). But the price is at least 1.5
Few people will like the American dollar... On the other hand, 1488 and 1489 in
There is no price list at all.
I provide the pinout of microcircuits 1488 and 1489, I don’t have the pinout for MAX-232
hand.
receiver: transmitter:
+-----------+ +-----------+
| | | |
1A -o1 14o- VCC VEE -o1 14o- VDD
| | | |
1C -o2 13o- 4A 1A -o2 13o- 4A
| | | |
1Y -o3 12o- 4C 1Y -o3 12o- 4B
| | | |
2A -o4 1489 11o- 4Y 2A -o4 1488 11o- 4Y
| | | |
2C -o5 10o- 3A 2B -o5 10o- 3A
| | | |
2Y -o6 9o- 3C 2Y -o6 9o- 3B
| | | |
GND -o7 8o- 3Y GND -o7 8o- 3Y
| | | |
+-----------+ +-----------+
Signal designation for the receiver (1489): A -- RS232 input, C -- control
hysteresis (TTL input), Y -- TTL output, VCC -- +5 volt power supply.Signal designations for the transmitter (1488): A, B -- TTL inputs, Y -- output
RS232, VDD -- +12 volt power supply, VEE -- -12 volt power supply. GND is common everywhere
wire
The transmitter chip implements logical function conjunctions, below is the table
truth:
A input | B entrance | Y output
--------+--------+---------
0 | 0 | VDD
--------+--------+---------
0 | 1 | VDD
--------+--------+---------
1 | 0 | VDD
--------+--------+---------
1 | 1 | VEE
note: it is assumed that the missing input 1B is connected to logic 1.
If the transmitter chip will only be used for TTL negotiation
outputs with an RS232 interface, then the unused inputs of the transmitter should
submit log.1. (according to the truth table, otherwise signal transmission
through a microcircuit will be impossible).
I have no information on using the “hysteresis control input”.
At the receiver input, capacitors with a capacity of several
tens of nanofarads, apparently to suppress the “bounce” of the signal. (required here
clarification).
In the absence of microcircuits 1488 and 1489, you can match the signals with
using a number of discrete elements. So much simplified receiver circuit
consists of only two diodes (you just need to take into account signal inversion):
+ VCC (+5 volts)
|---
/\n
-----
|
RS232 input -------+--------> TTL input
|
---
/\n
-----
|
-----GND
For a flow control circuit (5-wire cable), two such circuits are needed to
TD and RTS signals.
In case of extreme simplification, a direct connection of the TTL output to RS232 is possible
input (you only need to take into account the signal inversion). It will most likely be
work on most modern IBM-PC computers, but when connected to
other equipment may cause problems. The fact is that some
modern RS232 receivers consider a signal level less than +3 volts to be log. 1.
If direct connection is not desired, then a simple circuit can be used
transistor transmitter, such as that implemented in the ZS-Scorpion computer for
Connecting a serial printer:
+--------+ +5..12 volts
| |
- |
1.5k| | |
|_| |
| b|/ e
+------| KT361A
| | to
- |
560ohm| | -
|_| | | 560ohm
1.5k | |_|
TTL ____ b|/ to |exit --|____|--| KT315A +---+---> RS232 output
| e | |
| - |
--- GND | | --- 180pf
|_| ---
2.7k | |
+---+- -5..12 volts
For a flow control circuit (5-wire cable), two such circuits are needed to
TD and RTS signals.
The ZS-Scorpion computer already has one output and one RS232 input for
connecting a printer with a serial interface (signals "DSR" and "RS232" on
system connector). To implement an interface with flow control signals, you need
another entrance and another exit. Can use unused bit 5 of port
joystick kempston for input, and one of the unused bits of the FE port (bits 5,
6 and 7) for output. If you plan to use for signal matching
special microcircuits, it is better to put all signals there, and transistors and
Remove the diodes from the board. Or, as an option, the above circuits with diodes and
transistors only for unmatched signals.
Total two out of three options (multi-card, 580BB51, software emulation)
I described the connections sort of like this. For software emulation, the driver remains. Here
he:
The raw version (driver piece) is designed for a speed of 38400 bps:
;---------------------------------------
; RS232 EMULATOR ZX-LINK
;
TXPORT EQU #CFF7
RXMAX EQU 270
ZXL_INI LD A,1 JR ZXL_CTL
ZXL_OFF XOR A
ZXL_CTL ;LD (ZXL_DCD),A
AND #01
RLCA
RLCA
LD (TXMASK),A
IN A,(#1F)
RLCA
RLCA
RLCA
AND #01
RET
; LINE SCAN BC=SIZE D=SPEED CY=NOTHING
LSCAN DI
PUSH IX
PUSH IY
LD HL,RXMAX
LD DE,RXBYTE
PUSH DE
LD IX,(M_BUFF)
LD IY,TXMASK
LD BC,TXPORT
LD A,(TXMASK)
OR #20
OUT (C),A
RXNEXT LD D,#9F ; TIME
RXWAIT IN A,(#FE)
RLA
RET C
IN A,(#FE) ; 25..34 ~40
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
DEC D
JP NZ,RXWAIT ; +14
IN A,(#FE)
RLA
RET C
LD A,(TXMASK)
LD E,A ; +17
IN A,(#FE)
RLA
RET C
OUT (C),E ; +12
IN A,(#FE)
RLA
RET C
LD D,#7 ; +7
IN A,(#FE)
RLA
RET C
RXWAIT1 IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
DEC D
JP NZ,RXWAIT1
RXEND POP BC
EX DE,HL
LD HL,RXMAX
OR A
SBC HL,DE
POP IY
POP IX
JR NZ,RXOK
LD BC,#0101
XOR A
INC A
SCF
RET
RXOK LD D,LINKSPEED
LD B,H
LD C,L
XOR A
INC A
RET
RXBYTE IN A,(#FE)
RLA
JR C,RXBYTE1
DEC SP
DEC SP
JP RXWAIT
RXBYTE1 JR $+2
JR $+2
JR $+2
JR $+2
NOP
IN A,(#FE) ; B0
RLA
RR E
DEC HL
LD A,H
OR L
CP 1
SBC A,A
CPL
AND #20
OR (IY)
OUT (C), A
IN A,(#FE) ; B1
RLA
RR E
LD BC,RXBYTE
PUSH BC
LD BC,TXPORT
JR $+2
JR $+2
JR $+2
IN A,(#FE) ; B2
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B3
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B4
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B5
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B6
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B7
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B STOP
RLA
JR C,RXERR
LD A,E
CPL
LD (IX),A
INC IX
JP RXNEXT
RXERR LD A,(TXMASK)
OUT (C),A
JP RXEND
; SEND BLOCK IN MDMBUFF BC=SIZE
LTRANS DI
PUSH IX
LD E,C
LD D,B
LD IX,(M_BUFF)
LD BC,TXPORT
TXBYTE LD A,(TXMASK)
OR #08
OUT (C),A
LD A,(IX)
CPL
LD L,A
LD H,8
JR $+2
LD A,0
TXBIT RR L
SBC A,A
AND #08
OR 0
TXMASK EQU $-1
OUT (C),A
JP $+3
JP $+3
JP $+3
LD A,0
DEC H
JR NZ,TXBIT
JR $+2
LD A,0
LD A,(TXMASK)
OUT (C),A
JR $+2
JR $+2
JR $+2
INC IX
DEC DE
LD A,D
OR E
JR NZ,TXBYTE
LD B,4
DJNZ$
POP IX
RET
Unfortunately, there is one error here that does not manifest itself in any way when done correctly.
operation of the PC COM port but potentially very dangerous (as always
buffer overflow). The error there is that after filling
receiving buffer, Spectrum resets CTS so that the PC stops transmitting, after
this Spectrum receives the last byte (CTS signal blocks transmission
next byte, but the current one has already begun to be transmitted). It's just in process
When receiving the last byte, the Spectrum does not receive one byte, but how many they give.
The pisyuk usually doesn’t give more than one, but if it does, the Spectrum will
accept to the bitter end. In this case, the criterion for the end of transmission for
Spectrum serves as a long stop bit, that is, a pause in transmission of several bits
intervals. I'll definitely fix this bug, I'm just too lazy now, I'm tired of it
write a letter (>32kb already)...
Now regarding the encoding of information in the serial interface.
Log.0. coded voltage +3..+12 volts, logic 1. -3..-12 volts. Data
are transmitted sequentially, starting from 0-bit and ending with the last. There are several
standard sending formats: 5,6,7 or 8 data bits, 1 or 0 parity bits
(or odd), 1 or more stop bits. Stop bit, same as start bitdefinitely there. Usually they use the 8N1 format, that is, start bit, 8 data bits,
no parity and one (or more) stop bits. With 8 data bits controls
parity is not possible. In the 8N1 format, only 10 bits are transmitted for 8 information bits,
that is, 20% of the channel capacity is lost. In an inactive state,
when nothing is transmitted, the TD signal is in the log.1 state. (this means
pause). If the TD signal is long (more than one byte transmission)
is in log.0 state. then a sign of a wire break is formed. Transfer
starts with the start bit -- transmitted during one bit interval
log.0., all information bits are transmitted sequentially (one interval
by one bit), then the parity bits (if any) and then the proper number
stop bits (at least one, sometimes 1, 1.5, 2...) which are encoded by log.1.
The time period allocated for the bit interval is defined as the value
inversely proportional to speed. For example, at a speed of 38400 bps
(which is used in my source) the length of the bit interval is
26.0416 microseconds or 91.1456 Z80 processor cycles at clock speed
3.5Mhz. When transmitting 10 bits of data (byte in 8N1 format), the mismatch
speeds cannot be more than 5%, and for reliable reception even less -
It must be taken into account that the signal in the cable is affected by various distortions. Receivercan detect and signal certain errors. There are a number
standard speeds supported by most devices: 50, 75, 110, 150,
300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200 bps.
On the Spectrum, without turbo mode, the achievable maximum is 38400 bits per second --
the limitation is imposed by the algorithm of the receiver (see source). C
turbo mode at 7MHz will be 57600, but the program needs to be adjusted to
specific implementation of turbo mode - it’s easier to turn it off for a while
reception and transmission.
Transferring files between ZX and PC can be done using the program
MMD (aka MacroMoDem) on Spectrum (together with a special modem driver,
supports your interface type, a compatible one must be used on the PC
program (XMD for example). It is possible to use other Spectrum
terminals (for example Melon - the source code was lying around somewhere, you can use any interface
screw), and on the PC X,Y,Z modem. If the task is to transfer files, then
IMHO it is better to use MMD - it can be programmed for
automatic operation. If you need to control the PC in the console (for example, in
Linux) then it would be better to use an ANSI or at least a BT VT52 compatible terminal,
capable of receiving files using the Z-modem protocol. Could be a good option
using Melon (may need adaptation to your interface). Yesfragments from CP/M, I think I implemented VT52 there, but Z-modem is there naturally
no. Perhaps another ANSI terminal will appear... Idk. Without the Internet there is no point.
For now, the best option for you is MMD and Melon. Then maybe telnet
(ansi/vt220 terminal) and network... Without a network there will be no virtual disks. Although...
MAS for MMD emulated a turbojet engine on a PC via a link. But this is only inside MMD.
As I understand it, at least 2 people are currently working on the network issue
(groups) in the exUSSR and several foreigners. Everything is separate. Already have zxtcp,
zsock, uip, cpcip... someone threw something into zx.spectrum... IMHO the process is needed
just push hard in that direction.
In general, you have the task of choosing an interface: modems, multicards,
580ВВ51, emulation, maybe something else... all consistent. And parallel to
The PC will only have support in self-written programs and therefore
has no prospects (and RS232 also already has a place in the museum, it’s just that a lot has been done, but
Now USB rules).
I hope Lara won’t choke on your 36kb letter? Looks like there are some pissy glitches there
no, you shouldn't.
-+- [ZX]
+ Origin: Eat some more of these soft French rolls and drink some tea (2:5030/827.2)
================================================================================
Press RESET immediately, All!
================================================================================
* Forwarded by Kirill Frolov (500:812/1.507)
* Area : NETMAIL (My soap)
* From : Kirill Frolov, 2:5030/827.2 (27 Nov 02 22:11)
*To: Yuri Potapov
* Subj : 3.5" drive connection
================================================================================
Press RESET immediately, Yuri!
26 Nov 02 21:11, Yuri Potapov wrote to Kirill Frolov:
YP> in this case I have this idea
YP> on one side there is a green ZS Scorpion, there is no confusion
YP> on the other hand, not a very sophisticated PC running Linux
YP> most likely, the PC will have a CD, 1.44 drive, screw, modem
YP> but in general it should act as a server from/where I will download
YP> files
YP> modem emulation is not needed
YP> much of what I will transmit should go as commands
YP>console
YP> the spec will have to play the role of a client, including how I do
YP> explained that it is possible to surf the Internet via Linux using
YP> regular terminal
That is, you need either a network (telnet, ssh...), which does not exist, or a connectionvia serial port (Spectrum terminal emulation). Usually remote
control of a machine via a unix terminal is only possible via a network or
serial interface (modem).
YP> and this will already be more promising than trying to write in Spec now
YP> browser and tcp/ip and so on
Well, it’s for such purposes, IMHO, that you need to write. Only with a view to
using the resources of a pussy that is not in the next room, but accessible
via the Internet. For example, try telneting cyberspace.org - you can get
account on a machine running SunOS and use it to access other
network information resources.
There is no network on the Spectrum yet, well, at least there is definitely no telnet there.
Therefore, there are two options left for you: ZX <- serial interface -> PC.
The role of a “serial interface” can be either a cable or a pair
modems.
If you already have an ISA modem installed on your Spectrum, then just connect
you will receive a multicard from the PC and you will receive a serial port. If you need
parallel and modem, or do you need several serial ports then
you will have to think about upgrading the modem connection circuit. If the modem is on
Spectrum is not available, that is, there are 2 options: through a multicard (for example, by
Kondratiev scheme) and through software emulation of asynchronousSpectrum serial interface. In case of software emulation it is not necessary
The piss multicard is already in short supply.
The "minimal" null modem cable for connecting two computers contains
just three wires:
ZX PC
----------------- -----------------
signal DB9S DB25S signal DB9S DB25S
TD 3 2 <----------> RD 2 3
RD 2 3 <-----------> TD 3 2
GROUND 5 7 <-----------> GROUND 5 7
Columns DB9S and DB25S indicate the pin numbers on the corresponding
connectors.
There are several standard connectors for this interface, and most
popular ones are DB9S and DB25S (the letter S means Socket, that is, a socket. This
connectors with “holes” on the cable and with “pins” on the computer). In modern
IBM PC computers usually use DB9.
The minimum cable version has some disadvantages, in particular it
provides only software flow control, which is completely unsuitable for
use in the case of software emulation of a serial interface on
Spectrum (Spectrum can only receive data in a port polling cycle, but when
in the absence of other signal wires, he cannot in any way communicate to another
whether the computer is ready to receive it or not). In case of hardware implementationinterface on the Spectrum, the use of a 3-wire cable is also undesirable,
since it is difficult for Spectrum with its slowness to guarantee timely
extracting received data from the receiver buffer. Mentioned disadvantage
There is no 3-wire cable in the 4-wire or 5-wire interface, where
hardware flow control is used:
ZX PC
----------------- -----------------
signal DB9S DB25S signal DB9S DB25S
TD 3 2 <----------> RD 2 3
RD 2 3 <-----------> TD 3 2
RTS 7 4 <-----------> CTS 8 5
* CTS 8 5 <--(*)------> * RTS 7 4
GROUND 5 7 <-----------> GROUND 5 7
The signal marked with an asterisk '*' in the case of a 4-wire interface may not be
be used, but its non-use is undesirable: this signal provides
protection against overflow of the receiver buffer in the PC, just like a signal does
RTS for Spectrum.
5-wire interface provides a complete full-duplex transmission channel
information with hardware flow control. But if it is necessary to transmit
some control information outside the transmission channel, for example
ready/unready, reset/handshake, as often used in
modems, then you need a full-fledged interface consisting of 9 wires:ZX PC
----------------- -----------------
signal DB9S DB25S signal DB9S DB25S
TD 3 2 <----------> RD 2 3
RD 2 3 <-----------> TD 3 2
RTS 7 4 <-----------> CTS 8 5
CTS 8 5 <-----------> RTS 7 4
DTR 4 20 <--------+--> DSR 6 6
DSR 6 6 <--+-----)--> DTR 4 20
* DCD 1 8 <--+ +--> DCD 1 8
* RI 9 22 RI 9 22
GROUND 5 7 <-----------> GROUND 5 7
Signals marked with asterisks ('*') RI and DCD are used only in modems.
RI is an input at the terminal (computer) indicating the arrival of a call, DCD
signals the establishment of communication (presence of carrier). In this case, RI is not
is used, and the DCD is connected to the DTR signal from the remote side, which
provides "carrier appearance" when signaling the readiness of the remote side.
This was the wiring of a full-fledged null modem cable. She doesn't
coincides with the wiring of a regular modem cable!
In your case, I would use a 5-wire interface. As
cable, if it is impossible to get it ready-made, it is better to take a modem cable and
make a special adapter. I do not recommend making a cable
yourself, it’s better to take a ready-made one.In a modem cable, all signals are connected one to one, and in a null modem
reception and transmission signals, RTS-CTS, DTR-DSR are swapped. Below is
complete pinout of the serial interface. There are several standards
here we mean the RS-232C interface, used in most
personal computers.
Designation Connector contact Direction
RS232 DB9 DB25 output
PG - 1 - protective ground
(protect ground)
TD 3 2 output data transmission
(transmit data)
RD 2 3 input data reception
(receive data)
RTS 7 4 output request transfer
(request to send) data
CTS 8 5 input ready for
(clear to send) data reception
DSR 6 6 input ready
(data set ready) devices
data transmission
SG 5 7 - signal
(signal ground) common wire
DCD 1 8 input detection
(data carrier detected) carrier
DTR 4 20 output ready
(data terminal ready) terminalRI 9 22 input bell
(ring indicator)
Historically, although it no longer makes much sense,
that all devices using the RS-232C interface are divided into 2 types: devices
data transmission (DCE == Data Connection Equipment, e.g. modems) and final
equipment, terminals (DTE == Data Terminal Equipment, for example, when
When connecting a modem to a computer, the computer plays the role of a terminal). In fact
both devices are equivalent, but from this division they are designated differently
signals: DTR or DSR, RTS or CTS... and there is a little confusion. So here it is
the above table refers to DTE devices, that is, terminals
(computers). The pin numbers for DTE devices are correct, but for DCE
devices (modems) must be swapped TD and RD, CTS and RTS, DSR and DTR.
Hence, by the way, the difference between “straight” modem cables and “twisted” ones
null modem. And besides, in the table above there are only
signals used in the IBM-PC and most other computers. Full version
interface defines a larger number of signals on the DB25 connector.
When connecting an ISA multicard from an IBM-PC computer, problems may arise.
problems with connecting the remote connector cable ("miscarriage") to the multicard.
The fact is that there are several different options for pinout of contacts onmultimap. Here are the main ones:
Contact on the multicard Contact on the connector
Var.1 Var.2 Var.3 Var.4 DB9 DB25
(10) (10) (10) 1 - 1
3 5 3 3 3 2
2 3 4 5 2 3
7 4 8 7 7 4
8 6 7 9 8 5
6 2 9 11 6 6
5 9 1 13 5 7
1 1 5 15 1 8
4 7 2 14 4 20
9 8 6 18 9 22
Version 1 8-bit multicard loop
Ver.2 loop of 16-bit multicards
Version 3 cable for ports integrated on the motherboard
Version 4 wide cable to 25-pin connector
From everything written about how a multicard is connected, for example, by
Kondratiev's scheme should already be clear. Naturally, the ISA slot should
3 voltages are supplied: -12 volts, +12 volts, and +5 volts. Herself
The Kondratiev diagram for connecting an ISA modem (multi-card) to the Spectrum is here:
Original Kondratieff adapter circuit for connection
internal modem.
DD1
__ +---+
RD -----------------+1 | _____
| +------- IORD# (modem)
+---+ |
DD1 | +---+
+---+ |
A4 ----+1 | |
____ | +----+
IORQ --+ | |
+---+ | DD1 | +---+
+---+1 | _____
__ | +---+-- IOWR# (modem)
WR -----------------+ | |
+---+ |
|
+--------------------+
|
| DD2
| +--------+
+5v - | ---o R |
| | Q +-----+
+----/ C | |
| | |
A11 --------> D _ | |
_____ | Q O-- |
RESET --+---o S | |
| +--------+ |
| |
| DD3 |
| +---+ |
| |1 | |
+----+ O--------------- RESET (modem)
| | |
+---+ |
|
|
|
| DD1
DD3 | +---+
+---+ +--+1 | ---
|1 | | +------ NMI
(modem) IRQ4 ----+ O---------+ |
| | +---+
+---+
A8 ------------------- A0 (modem)
A9 ------------------- A1 (modem)
A10 ------------------- A2 (modem)
D0..D7 ---------------- D0..D7 (modem)
+5v -------------------- A3..A10 (modem)
GND -------------------- AEN (modem)
List of elements:
DD1 1533LL1
DD2 1533TM2
DD3 1533ЛH1
Signals marked in brackets "(modem)" are connected to
corresponding pins of the ISA slot for the modem, the rest
the signals are connected directly to the computer bus.
Accessing modem registers via ports
The modem registers are accessible through the microprocessor I/O ports.
The address is calculated like this:
0xF0EF + (0x0800 if NMI interrupts are disabled) + (register_address*0x100)
The interrupt enable trigger from the modem switches only when
output to the modem ports.
NOTE: Instead of non-maskable (NMI), you can use maskable
(INT) interrupt. Not all programs support this yet, but THIS IS MORE
CORRECT DECISION. THE USE OF NMI CAN POTENTIALLY RESULT IN
STACK OVERFLOW AND DISRUPTION OF NORMAL OPERATION OF PROGRAMS.
Just in case, I’m also bringing a modified one (so that it doesn’t work with the 7FFD port).
conflicted) Shepelev’s scheme:
Modified Shepelevsky scheme, supported in the Melon program.
D0..D7 ----------------------- D0..D7 (modem)
A8 -------------------------- A0 (modem)
A9 -------------------------- A1 (modem)
A10 -------------------------- A2 (modem)
A11 -------------------------- A3 (modem)
A12 -------------------------- A8 (modem)
A13 -------------------------- A9 (modem)+5v ---------------------- A4 (modem)
+5v ---------------------- A5 (modem)
GND ----------------------- AEN (modem)
+---+
A14 --------+ 1 |
| +---+
A15 --------+ | |
+---+ |
DD1.1 | +---+
+--+ 1 |
| o----+---- A7 (modem)
A6 ---------------------+ | |
+---+ +---- A6 (modem)
DD2.1
____ +---+
IORQ ----+---+ 1 |
__ | | +----------- IORD# (modem)
RD -----(---+ |
| +---+
| DD1.2
| +---+
+---+ 1 |
__ | +----------- IOWR# (modem)
WR ---------+ |
+---+
DD1.3
+---+
GND -----+ 1 |
_____ | o----------RESET (modem)
RESET -------+ |
+---+
DD2.2
Read more:
DD1 1533ЛЛ1
DD2 1533ЛЕ1
Read the story of the story
The story of the story of the story of the story микропроцессора,
Read more about the article:
0x38BF + адрес_регистра_модема
In the end the story was written. использование прерыванийfrom the modem, but this feature can be added by connecting one of the outputs
modem interrupts via an inverter with an "open collector" output
(chip 555ЛH2) with an INT signal (maskable interrupt) on the bus
ZX-Spectrum. An NPN bipolar transistor can act as an inertor
(for example KT315) in the corresponding connection circuit.
The above schemes have some disadvantages. For example, they
most likely will not work if you connect the modem and
computer with long (>10cm) wires. The whole problem here is
excessive inductance of conductors. If the modem does not work, you can
try passing signals A8,A9,A10,IOWR and IORD through the trigger
Schmidt installed in close proximity to the ISA slot or through
resistors with a resistance of 30-50 ohms.
Pin assignments of the short (8-bit) ISA slot:
+---------+---------------+-----------------+---------+
| contact | signal | signal | contact |
+-+-----+-+---------------+-----------------+-+-----+-+
| A1 | IOCHK | GND | B1 |
+-----+-----------------+-------------------+-----+
| A2 | D7 | RESET | B2 |
+-----+-----------------+-------------------+-----+
| A3 | D6 | +5v | B3 |
+-----+-----------------+-------------------+-----+
| A4 | D5 | IRQ2/9 (*) | B4 | +-----+-----------------+-------------------+-----+
| A5 | D4 | -5v | B5 |
+-----+-----------------+-------------------+-----+
| A6 | D3 | DRQ2 | B6 |
+-----+-----------------+-------------------+-----+
| A7 | D2 | -12v | B7 |
+-----+-----------------+-------------------+-----+
| A8 | D1 | OWS2# | B8 |
+-----+-----------------+-------------------+-----+
| A9 | D0 | +12v | B9 |
+-----+-----------------+-------------------+-----+
| A10 | IOCHDRY | GND | B10 |
+-----+-----------------+-------------------+-----+
| A11 | AEN | SmemWR# | B11 |
+-----+-----------------+-------------------+-----+
| A12 | A19 | SmemRD# | B12 |
+-----+-----------------+-------------------+-----+
| A13 | A18 | IOWR# | B13 |
+-----+-----------------+-------------------+-----+
| A14 | A17 | IORD# | B14 |
+-----+-----------------+-------------------+-----+
| A15 | A16 | DACK3# | B15 |
+-----+-----------------+-------------------+-----+
| A16 | A15 | DRQ3 | B16 |
+-----+-----------------+-------------------+-----+
| A17 | A14 | DACK1# | B17 |
+-----+-----------------+-------------------+-----+
| A18 | A13 | DRQ1 | B18 |
+-----+-----------------+-------------------+-----+
| A19 | A12 | REFR# | B19 |
+-----+-----------------+-------------------+-----+
| A20 | A11 | BClock | B20 |
+-----+-----------------+-------------------+-----+
| A21 | A10 | IRQ7 | B21 |
+-----+-----------------+-------------------+-----+
| A22 | A9 | IRQ6 | B22 |
+-----+-----------------+-------------------+-----+
| A23 | A8 | IRQ5 | B23 |
+-----+-----------------+-------------------+-----+
| A24 | A7 | IRQ4 | B24 |
+-----+-----------------+-------------------+-----+
| A25 | A6 | IRQ3 | B25 |
+-----+-----------------+-------------------+-----+
| A26 | A5 | DACK2# | B26 |
+-----+-----------------+-------------------+-----+
| A27 | A4 | TC | B27 |
+-----+-----------------+-------------------+-----+
| A28 | A3 | BALE | B28 |
+-----+-----------------+-------------------+-----+
| A29 | A2 | +5v | B29 |
+-----+-----------------+-------------------+-----+
| A30 | A1 | OSC | B30 |
+-----+-----------------+-------------------+-----+
| A31 | A0 | GND | B31 |
+-----+-----------------+-------------------+-----+
Note: some modem (multi-card) models are designed
to connect to long (16-bit)
ISA slot. You can connect them without any problems
and into a short slot when used
interrupts in the range IRQ1..IRQ7.
NOTE: Instead of the Non-Maskable Interrupt (NMI) used in
Kondratiev circuit, you can use a maskable (INT) interrupt. Not yet
all programs support this, but THIS IS A MORE CORRECT SOLUTION. USE
NMI CAN POTENTIALLY RESULT IN A STACK OVERFLOW AND INTERRUPTION OF NORMAL
PROGRAM OPERATIONS.
Everything should be clear by now with connecting ISA multicards and modems. Remaining
two more options: a serial port based on i8251 (K580VV51) - if necessary
I’ll find a diagram, but there’s a lot of soldering required, and the speed is only 9600. And another option is this
software emulation of a serial interface. Everything is here in terms of soldering
much simpler, you need two software-controlled ports (you need two binary
discharge) on the output and two ports on the input. If you plan to useinterface without flow control, you can get by with one output port and one
at the entrance. But this is a very unreliable solution; it requires the use of special
data transfer protocols that guarantee error-free data transfer. Yes
Another option is using flow control only in the direction from PC to ZX
(see above, 4-wire interface), but it’s still better to use a full-fledged
5-wire interface. Let's say we already have two output ports, two ports
at the entrance. The ports are based on TTL logic, that is, they transmit binary signals with
levels from 0 to +5 volts. They must be coordinated with the RS-232C interface. Below
there is a table explaining the coding of signals in TTL logic and interface
RS-232C:
Signal TTL logic RS-232C
-----------------------------------
log. 0. 0..1.5 volts +3..12 volts
log. 1. 2..5 volts -3..-12 volts
Coordination is best accomplished using specially designed
this microcircuit (imported): receiver - 1489, transmitter - 1488. There are
and Soviet analogues of these microcircuits, but I don’t remember their designations. There is also
newer and easier-to-use microcircuits that allow TTL matching
logic with RS-232C interface, for example MAX-232. Convenience lies in
no need to have a power source with a voltage of -12 and +12 volts(generated inside the microcircuit, on capacitors). But the price is at least 1.5
Few people will like the American dollar... On the other hand, 1488 and 1489 in
There is no price list at all.
I provide the pinout of microcircuits 1488 and 1489, I don’t have the pinout for MAX-232
hand.
receiver: transmitter:
+-----------+ +-----------+
| | | |
1A -o1 14o- VCC VEE -o1 14o- VDD
| | | |
1C -o2 13o- 4A 1A -o2 13o- 4A
| | | |
1Y -o3 12o- 4C 1Y -o3 12o- 4B
| | | |
2A -o4 1489 11o- 4Y 2A -o4 1488 11o- 4Y
| | | |
2C -o5 10o- 3A 2B -o5 10o- 3A
| | | |
2Y -o6 9o- 3C 2Y -o6 9o- 3B
| | | |
GND -o7 8o- 3Y GND -o7 8o- 3Y
| | | |
+-----------+ +-----------+
Signal designation for the receiver (1489): A -- RS232 input, C -- control
hysteresis (TTL input), Y -- TTL output, VCC -- +5 volt power supply.Signal designation for the transmitter (1488): A, B -- TTL inputs, Y -- output
RS232, VDD -- +12 volt power supply, VEE -- -12 volt power supply. GND is common everywhere
wire
The transmitter chip implements logical function conjunctions, below is the table
truth:
A input | B entrance | Y output
--------+--------+---------
0 | 0 | VDD
--------+--------+---------
0 | 1 | VDD
--------+--------+---------
1 | 0 | VDD
--------+--------+---------
1 | 1 | VEE
note: it is assumed that the missing input 1B is connected to logic 1.
If the transmitter chip will only be used for TTL negotiation
outputs with an RS232 interface, then the unused inputs of the transmitter should
submit log.1. (according to the truth table, otherwise signal transmission
through a microcircuit will be impossible).
I have no information on using the “hysteresis control input”.
At the receiver input, capacitors with a capacity of several
tens of nanofarads, apparently to suppress the “bounce” of the signal. (required here
clarification).
In the absence of microcircuits 1488 and 1489, you can match the signals with
using a number of discrete elements. So much simplified receiver circuit
consists of only two diodes (you just need to take into account signal inversion):
+ VCC (+5 volts)
|---
/\n
-----
|
RS232 input -------+--------> TTL input
|
---
/\n
-----
|
-----GND
For a flow control circuit (5-wire cable), two such circuits are needed to
TD and RTS signals.
In case of extreme simplification, a direct connection of the TTL output to RS232 is possible
input (you only need to take into account the signal inversion). It will most likely be
work on most modern IBM-PC computers, but when connected to
other equipment may cause problems. The fact is that some
modern RS232 receivers consider a signal level less than +3 volts to be log. 1.
If direct connection is not desired, then a simple circuit can be used
transistor transmitter, such as that implemented in the ZS-Scorpion computer for
Connecting a serial printer:
+--------+ +5..12 volts
| |
- |
1.5k| | |
|_| |
| b|/ e
+------| KT361A
| | to
- |
560ohm| | -
|_| | | 560ohm
1.5k | |_|
TTL ____ b|/ to |exit --|____|--| KT315A +---+---> RS232 output
| e | |
| - |
--- GND | | --- 180pf
|_| ---
2.7k | |
+---+- -5..12 volts
For a flow control circuit (5-wire cable), two such circuits are needed to
TD and RTS signals.
The ZS-Scorpion computer already has one output and one RS232 input for
connecting a printer with a serial interface (signals "DSR" and "RS232" on
system connector). To implement an interface with flow control signals, you need
another entrance and another exit. Can use unused bit 5 of port
joystick kempston for input, and one of the unused bits of the FE port (bits 5,
6 and 7) for output. If you plan to use for signal matching
special microcircuits, it is better to put all signals there, and transistors and
Remove the diodes from the board. Or, as an option, the above circuits with diodes and
transistors only for unmatched signals.
Total two out of three options (multi-card, 580BB51, software emulation)
I described the connections sort of like this. For software emulation, the driver remains. Here
he:
The raw version (driver piece) is designed for a speed of 38400 bps:
;---------------------------------------
; RS232 EMULATOR ZX-LINK
;
TXPORT EQU #CFF7
RXMAX EQU 270
ZXL_INI LD A,1 JR ZXL_CTL
ZXL_OFF XOR A
ZXL_CTL ;LD (ZXL_DCD),A
AND #01
RLCA
RLCA
LD (TXMASK),A
IN A,(#1F)
RLCA
RLCA
RLCA
AND #01
RET
; LINE SCAN BC=SIZE D=SPEED CY=NOTHING
LSCAN DI
PUSH IX
PUSH IY
LD HL,RXMAX
LD DE,RXBYTE
PUSH DE
LD IX,(M_BUFF)
LD IY,TXMASK
LD BC,TXPORT
LD A,(TXMASK)
OR #20
OUT (C),A
RXNEXT LD D,#9F ; TIME
RXWAIT IN A,(#FE)
RLA
RET C
IN A,(#FE) ; 25..34 ~40
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
DEC D
JP NZ,RXWAIT ; +14
IN A,(#FE)
RLA
RET C
LD A,(TXMASK)
LD E,A ; +17
IN A,(#FE)
RLA
RET C
OUT (C),E ; +12
IN A,(#FE)
RLA
RET C
LD D,#7 ; +7
IN A,(#FE)
RLA
RET C
RXWAIT1 IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
IN A,(#FE)
RLA
RET C
DEC D
JP NZ,RXWAIT1
RXEND POP BC
EX DE,HL
LD HL,RXMAX
OR A
SBC HL,DE
POP IY
POP IX
JR NZ,RXOK
LD BC,#0101
XOR A
INC A
SCF
RET
RXOK LD D,LINKSPEED
LD B,H
LD C,L
XOR A
INC A
RET
RXBYTE IN A,(#FE)
RLA
JR C,RXBYTE1
DEC SP
DEC SP
JP RXWAIT
RXBYTE1 JR $+2
JR $+2
JR $+2
JR $+2
NOP
IN A,(#FE) ; B0
RLA
RR E
DEC HL
LD A,H
OR L
CP 1
SBC A,A
CPL
AND #20
OR (IY)
OUT (C), A
IN A,(#FE) ; B1
RLA
RR E
LD BC,RXBYTE
PUSH BC
LD BC,TXPORT
JR $+2
JR $+2
JR $+2
IN A,(#FE) ; B2
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B3
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B4
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B5
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B6
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B7
RLA
RR E
JR $+2
JR $+2
JR $+2
JR $+2
JR $+2
NOP
NOP
IN A,(#FE) ; B STOP
RLA
JR C,RXERR
LD A,E
CPL
LD (IX),A
INC IX
JP RXNEXT
RXERR LD A,(TXMASK)
OUT (C),A
JP RXEND
; SEND BLOCK IN MDMBUFF BC=SIZE
LTRANS DI
PUSH IX
LD E,C
LD D,B
LD IX,(M_BUFF)
LD BC,TXPORT
TXBYTE LD A,(TXMASK)
OR #08
OUT (C),A
LD A,(IX)
CPL
LD L,A
LD H,8
JR $+2
LD A,0
TXBIT RR L
SBC A,A
AND #08
OR 0
TXMASK EQU $-1
OUT (C),A
JP $+3
JP $+3
JP $+3
LD A,0
DEC H
JR NZ,TXBIT
JR $+2
LD A,0
LD A,(TXMASK)
OUT (C),A
JR $+2
JR $+2
JR $+2
INC IX
DEC DE
LD A,D
OR E
JR NZ,TXBYTE
LD B,4
DJNZ$
POP IX
RET
Unfortunately, there is one error here that does not manifest itself in any way when done correctly.
operation of the PC COM port but potentially very dangerous (as always
buffer overflow). The error there is that after filling
receiving buffer, Spectrum resets CTS so that the PC stops transmitting, after
this Spectrum receives the last byte (CTS signal blocks transmission
next byte, but the current one has already begun to be transmitted). It's just in process
When receiving the last byte, the Spectrum does not receive one byte, but how many they give.
The pisyuk usually doesn’t give more than one, but if it does, the Spectrum will
accept to the bitter end. In this case, the criterion for the end of transmission for
Spectrum serves as a long stop bit, that is, a pause in transmission of several bits
intervals. I'll definitely fix this bug, I'm just too lazy now, I'm tired of it
write a letter (>32kb already)...
Now regarding the encoding of information in the serial interface.
Log.0. coded voltage +3..+12 volts, logic 1. -3..-12 volts. Data
are transmitted sequentially, starting from 0-bit and ending with the last. There are several
standard sending formats: 5,6,7 or 8 data bits, 1 or 0 parity bits
(or odd), 1 or more stop bits. Stop bit, same as start bitdefinitely there. Usually they use the 8N1 format, that is, start bit, 8 data bits,
no parity and one (or more) stop bits. With 8 data bits controls
parity is not possible. In the 8N1 format, only 10 bits are transmitted for 8 information bits,
that is, 20% of the channel capacity is lost. In an inactive state,
when nothing is transmitted, the TD signal is in the log.1 state. (this means
pause). If the TD signal is long (more than one byte transmission)
is in log.0 state. then a sign of a wire break is formed. Transfer
starts with the start bit -- transmitted during one bit interval
log.0., all information bits are transmitted sequentially (one interval
by one bit), then the parity bits (if any) and then the proper number
stop bits (at least one, sometimes 1, 1.5, 2...) which are encoded by log.1.
The time period allocated for the bit interval is defined as the value
inversely proportional to speed. For example, at a speed of 38400 bps
(which is used in my source) the length of the bit interval is
26.0416 microseconds or 91.1456 Z80 processor cycles at clock speed
3.5Mhz. When transmitting 10 bits of data (byte in 8N1 format), the mismatch
speeds cannot be more than 5%, and for reliable reception even less -
It must be taken into account that the signal in the cable is affected by various distortions. Receivercan detect and signal certain errors. There are a number
standard speeds supported by most devices: 50, 75, 110, 150,
300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200 bps.
On the Spectrum, without turbo mode, the achievable maximum is 38400 bits per second --
the limitation is imposed by the algorithm of the receiver (see source). C
turbo mode at 7MHz will be 57600, but the program needs to be adjusted to
specific implementation of turbo mode - it’s easier to turn it off for a while
reception and transmission.
Transferring files between ZX and PC can be done using the program
MMD (aka MacroMoDem) on Spectrum (together with a special modem driver,
supports your interface type, a compatible one must be used on the PC
program (XMD for example). It is possible to use other Spectrum
terminals (for example Melon - the source code was lying around somewhere, you can use any interface
screw), and on the PC X,Y,Z modem. If the task is to transfer files, then
IMHO it is better to use MMD - it can be programmed for
automatic operation. If you need to control the PC in the console (for example, in
Linux) then it would be better to use an ANSI or at least a BT VT52 compatible terminal,
capable of receiving files using the Z-modem protocol. Could be a good option
using Melon (may need adaptation to your interface). Yesfragments from CP/M, I think I implemented VT52 there, but Z-modem is there naturally
no. Perhaps another ANSI terminal will appear... Idk. Without the Internet there is no point.
For now, the best option for you is MMD and Melon. Then maybe telnet
(ansi/vt220 terminal) and network... Without a network there will be no virtual disks. Although...
MAS for MMD emulated a turbojet engine on a PC via a link. But this is only inside MMD.
As I understand it, at least 2 people are currently working on the network issue
(groups) in the exUSSR and several foreigners. Everything is separate. Already have zxtcp,
zsock, uip, cpcip... someone threw something into zx.spectrum... IMHO the process is needed
just push hard in that direction.
In general, you have the task of choosing an interface: modems, multicards,
580ВВ51, emulation, maybe something else... all consistent. And parallel to
The PC will only have support in self-written programs and therefore
has no prospects (and RS232 also already has a place in the museum, it’s just that a lot has been done, but
Now USB rules).
I hope Lara won’t choke on your 36kb letter? Looks like there are some pissy glitches there
no, you shouldn't.
-+- [ZX]
+ Origin: Eat some more of these soft French rolls and drink some tea (2:5030/827.2)
================================================================================
Press RESET immediately, All!