z80
[For readers' letters]
(C) WLODEK BLACK
KR580VV55A - Programmable ADAPTER
Parallel I / O
Hello, friends!
VV55 Once again we are vstrePA3 January 1940 PA4
chaemsya in the fields of your
messages! Epidemic myshiPA2 February 1939 PA5 Nogo rabies :-)
swept dobroPA1 March 1938 PA6 mu ten
"Profyakov" plus interest to the
problems April 1937 PA0 PA7 connecting different
peripherals (printers and
/ RD May 1936 / WR, etc.) and management called away to a life
free on / CS June 1935 Reset (+) necks conversation today.
Also among your Earth in July 1934 D0
bids came across Conc retnye request - rassA0 August 1933 D1
Prove of VV55.
A1 September 1932 D2 circuit KR580VV55A
as a logical ustroystPS7 October
1931 D3 is in the pro ble adapter paralPS6 November 30 D4 of
parallel I / O contains 3 8-bit
PS5 December 29 D5 port can work as a thief to enter and
PS4 13 28 D6 at the conclusion. As an electron LIMITED
component VV55 - miPS0 14 27 D7 kroshema n-MOS type, on the +5
V supply voltage; 15 26 PS1 +5 V input circuits are made
for MOSFETs with izoPS2 16 25 PV7
isolated gate, and you can chain gressorial pePS3 17 24 PV6
goes over into the third state of the. Input and output PV0 18
23 PV5 levels consistent with TTL.
Inputs chips PV1 19 22 PV4 sensitive to static electricity and
Scoma PV2 20 21 PV3 potential overload kam outside 0 .. +5 V
therefore should not be left "free hanging" inputs, which can
be anything to connect or disconnect (eg, Kempston joystick) -
need to connect these inputs to ground or +5 V through
resistors, the resistance of which little is critical (up to
several tens of kilo). Better yet, connect the peripherals are
not directly to the contacts VV55, and through the buffer
elements TTL-type, as this is done, for example, in printers -
a Schmitt trigger K155 TL2, for example. If your computer is
directly VV55 "communicates" with the outside world - exercise
extreme caution when connecting and disconnecting devices
associated with it, no matter stick it or a printer - turn off
the computer and another device, remove the plug from the
socket, get rid of your own static electricity even touching
the metal chassis slot tape input or to another details
connected to ground the computer, and then take a connecting
cable connector device and insert it in the right place! At the
same time the chip is much less sensitive to short-circuit
output to 0 or +5 volts, but such an overload and not be
allowed.
Software control VV55
The policy regarding VV55 represents 4 addressable port
in a standard configuration "Spectrum" (PROFI, Delta-C,
"Pentagon-48, etc.) with address # 1F, # 3F, # 5F and # 7F.
Address these Ports are defined by bits A5 and A6, address bus,
which connected the inputs A0 and A1 circuits through which
selected one or another internal register VV55 and discharge A7
Address Bus, which should be 0 for the sample VV55. That
corresponds to the address registers, internal adapter: # 1F -
Port A # 3F - Port B
# 5F - Port C
# 7F - control register.
VV55 can operate in three modes, different purpose
individual bits of ports and ports in general. In modes 1 and
2, the adapter is capable to a limited extent on their own to
support the protocols for transferring / receiving data, for
example, by issuing special flags or signals interrupt request,
under the which are allocated the appropriate lines of some
ports. For have these modes of little interest, as in
"Spectrum" their implementation is difficult and generally of
little use. In Mode 0 adapter works as a 3 parallel ports I / O
in which you can simply write or read from there. In Mode 0
ports A and B can be programmed either to enter or to withdraw
as an 8-bit registers, and port C is divided into two 4-bit
registers, each of which can either accept or transmit data.
Programming adapter is entering in control register 8-bit code,
the appointment of individual bits is as follows:
D7 D6 D5 D4 D3 D2 D1 D0
Mode Channel A Channel A Channel B Mode KanalC2 KanalC1
and channel C2 channels
1 0 0 1 - IN 1 - IN B and C1 1 - IN 1 - IN
(Mode 0) 0 - OUT 0 - OUT 0 0 - OUT 0 - OUT
Channel C1 - bits 0 ... 3 Port C;
channel C2 - level 4 ... 7 Port C.
In a typical embodiment of a control code is # 98:
% 10011000, and the port assignment is as follows: Port A -
Kempston joystick (input) port B - data for the printer
(output) channel C1 - Bit 0 - signal / STROBE for the printer
(output) channel C2 - bit 7 - signal BUSY (busy) from the
printer (input). After reset, all three ports are working on
putting in Mode 0, thus use of Kempston joystick is possible
without special programming adapter. Note: reset signal is fed
level logic 1! In older versions of chips, wearing name
K580IK55, reading from a port programmed as an output, let us
always # FF. In modern version VV55 result of reading is that
was recorded in the register of the adapter. This should be
borne in mind when acquainted with the old literature, for
example, with a description of the computer, "Radio-86RK. Most
recently, Moscow's network spread over the whole "epidemic of
murine rabies - programming glitches ZXZIP / ZXUNZIP computers
PROFI, when "discover" a nonexistent interface Kempston-mouse,
and on the screen started to randomly move the mouse pointer,
making it difficult work with the program from the keyboard.
Despite the fact that the ports mouse interface are
distinguished by addresses from VV55, participated in the
latest "reality" seems to have a place, as on lines A7 and A5
VV55 explicitly chosen by simulating the presence of some mouse
interface. I offered to users PROFI try this program from:
1910 OUT 127,128: OUT 31,255: OUT 63,255: OUT 95,255
20 RANDOMIZE USR 15619: REM: RUN "ZXZIP"
It is easy to establish that after a "procedure" read from the
ports of channels A, B and C will give a # FF, that is, it
might seem that these ports and there is no at all. Results of
the survey profistov showed that:
PROFI on 1-D and 3-x versions ZIP begins to work normally, if
ZIP-profievsky not (not "ZIPp");
UNZIP-s "cure" generally all;
PROFI on 5-x version bugs and so no.
But I myself do not PROFI, so a more thorough investigation
I could not hold.
And finally, bring the text of the print driver for the
ZX-Word-a:
ORG 23296; so it is necessary for the ZX-Word-a
NOP; so necessary for the ZX-Word-a
JR INIT
; NOP
START DI
LD E, A
CHROUT LD A, (23624); Border
CPL
RRCA
RRCA
RRCA
AND 7
OUT (254), A; visualization of output data
CHROU1 IN A, (# 5F)
RLCA; free?
JR NC, READY
OFFLIN CALL BREAK
JR CHROU1
READY LD A, E
OUT (# 3F), A; output bytes of data in channel B
XOR A
OUT (# 5F), A; / Strobe
READY1 IN A, (# 5F)
RLCA; Busy
JR C, RECEIV
CALL BREAK
JR READY1
RECEIV LD A, # 0F; remove / Strobe
OUT (# 5F), A
XOR A
OUT (# 3F), A
LD A, (23624)
RRCA
RRCA
RRCA
AND 7; simultaneously reset the flag C, which is necessary
for ZX-Word-a
OUT (254), A
RET
; BREAK CALL # 1F54; systemic Break
RET C
POP AF
CALL RECEIV
SCF; flag for the ZX-Worda, we want to stop printing
RET
; INIT DI
DEFB # C3; JP
INITA DEFW INIT0
INIT0 LD HL, INITW
LD (INITA), HL; hammered, then to re-
do not initialize VV55
LD A, # 98
OUT (# 7F), A; setting VV55
CALL RECEIV
INITW LD HL, STALST; a list of the initialization code printer
INIT1 LD A, (HL)
LD E, A
INC E
RET Z
CALL START
INC HL
JR INIT1
STALST DEFB 27,64,27,82,4,255; for MS-6312. For other prints
ditch do not need "27,82,4". ; DEFS 23,549 - $
END
;
[Continuing the theme of "assembler" should be].
