(C) Davydov VM
Nizhny Novgorod Region., S.Zaprudnoe.
Materials,
published in ZX REVIEW.
SOME ISSUES
Auto-BASIC PROGRAM.
(ZX REVIEW 94 / 5, p. 29).
The correspondent asked a question
the launch of the machine code BASIC-programs. According to
these suggestions do not be a problem, but it should be borne
in mind one subtlety.
Although mostly in BASIC
written long spouts 01.02
sector program in BASIC nobody forbade, and can
meet the program uses all the memory. Run it from
native code will not succeed. When
Upload it overwrite procedure
run. A boot, for which
it all meant and should run any program.
In addition, when using
BASIC to load and run
program in machine code need only pass the name of
file into a string BASIC Type:
CLEAR VAL "65535":
RANDOMIZE USR VAL "15619":
REM: RUN "ANY NAME"
in place and put ANY NAME
RET to return to BASIC, and all
Larry will do the rest
TR-DOS. The size of the program at
this fall.
Incidentally, the same restrictions
refer to the location in memory
relotsiruemoy procedure "LOADMERGE" (ZX REVIEW 96/4-5, p.80).
Summary: boots with the intermediate output of the BASIC
language written not of feeble mind, but for versatility.
REDEFINE KEYS
(ZX REVIEW 96/4-5, p.79).
Seeing in three places mask
% 11111, very much wanted
shorten the procedure. Source
option declined by only two
bytes. Simultaneously, increased
performance of six cycles
although the performance is not
required. All are equal before the survey, the following keys
have set retarding cycle or
procedure for releasing the standby
keys, or unwillingly,
You can assign a single key on the
all functions.
At the end of the procedure is added
a few lines to wait for a key is released. They are marked
commentary; ***
1410.
REDEF LD BC, # 7FFE
LD H, # 1F
KEY_L IN A, (C)
AND H
CP H
JR NZ, KEY_PR
RRC B
JR C, KEY_L
JR REDEF
KEY_PR XOR H
LD L, A
LD H, B
WAIT_L IN A, (C); ***
AND L; ***
JR Z, WAIT_L; ***
RET
2
If the procedure required performance, increase
him for one clock cycle would be if, instead of the sequence
CP H
JR NZ, KEY_PR
use
JP PE, KEY_PR
In addition to the previous
propose a variant of the procedure for determining the code key
was pressed. At the entrance to the procedure in the case H -
high byte address port, L - Mask bit down
keys. At the output of A - code key pressed. Modifies registers
HL and DE. HL - address in ROM of which is taken the code in
the battery; DE - offset from start of table
located at # 0205.
140.
TRANSF XOR A
LOOP_1 ADD A, # 08
RL L
JR NC, LOOP_1
LOOP_2 INC A
RL H
JR C, LOOP_2
SUB # 21
LD E, A
JP # 0347
Note. At # 0347
in ROM is the following snippet:
LD HL, # 0205
LD D, # 00
ADD HL, DE
LD A, (HL)
RET
Control keys in the table at # 0205 correspond to the
following codes:
# 0D - ENTER
# 0E - SYMBOL SHIFT
# E3 - CAPS SHIFT
2
The printing process
42 characters per line.
In ZX REVIEW 95 / 5 has been published how to print 42
characters per line (Dmitry Sergeev). In ZX REVIEW 96/4-5 shows
its simplified version (Matyushev Alexander).
Because they use
one algorithm, they share common
limitations.
First of all, not entirely correctly worked through
printing using color attributes. The calculation of the address
attributes is the left corner of familiarity 6x8 and if the
character is two familiarity 8x8, at the right
the color is painted, only the left
part of the symbol.
Eliminate this possible, for example, in this way. For
listing in the ZX 96/4-5, p. 102 between lines 0870 and 0880
insert the following snippet:
140.
LD A, (XTXT)
AND 3
JP PE, NO_INCX; transition to
3 line 0880
INC HL
LD A, (23659)
LD (HL), A
2
For a listing of the ZX 95 / 5,
p.30 similar piece to insert between lines 0133
and 0134.
The second limitation relates to
algorithm for printing. As used in the screen scrolling
memory clearing nearby familiarity, use this
procedure can only print on the blank screen from left to right
and top to bottom. For these purposes the procedure is quite
compact.
To make the procedure to change the universality of the
procedure PRSYM.
The algorithm can be, for example, so. It is clear from the
bit-layout 8x8 and familiarity 6x8 pixels.
Familiarity 8x8
1 2 3
765432 10 7654 3210 76 543210
765432 76 5432 7654 32 765432
1 2 3 4
Familiarity 6x8
For the first familiarity 6x8 bytes need to take the screen
corresponding to the first 8x8 familiarity, to impose on the
AND mask
% 00000011,
add to the result of OR byte of character generator and the
final result send to the screen in the first familiarity 8x8.
To print the second familiarity 6x8:
1. Get byte character generator.
2. Cyclic shift bits to obtain the following location:
54321076
3. The value obtained in
Clause 2, to impose on the AND mask:
% 00000011
4. Get byte screen corresponding to the first familiarity 8x8
and apply for AND mask
% 11111100
5. Combine the results of OR A.3 and A.4 and the resulting
value to send to the screen in the first familiarity 8x8.
6. The value obtained in
Clause 2, to impose on the AND mask
% 11110000
7. Get byte screen corresponding to the second familiarity 8x8
and apply for AND mask
% 00001111
8. Combine the results of OR A.6 and A.7 and the resulting
value to send to the screen in the second familiarity 8x8.
Printable third familiarity 6x8:
1. Get byte character generator.
2. Cyclic shift bits to obtain the following location:
32107654
3. The value obtained in
Clause 2, to impose on the AND mask:
% 00001111
4. Get byte screen corresponding to the second familiarity
8x8, and impose on the AND mask
% 11110000
5. Combine the results of OR A.3 and A.4 and the resulting
value to send to the screen in the second familiarity 8x8.
6. the value obtained in
Clause 2, to impose on the AND mask
% 11000000
7. Get byte screen corresponding to the third familiarity
8x8, and impose on the AND mask
% 00111111
8. Combine the results of OR A.6 and A.7 and the resulting
value to send to the screen in the third familiarity 8x8.
Printable fourth familiarity 6x8:
1. Get byte character generator.
2. Cyclic shift bits to obtain the following location:
10765432
3. The value obtained in
Clause 2, to impose on the AND mask:
% 00111111
4. Get byte screen corresponding to the third familiarity
8x8, and impose on the AND mask
% 11000000
5. Combine the results of OR A.3 and A.4 and the resulting
value to send to the screen in the third familiarity 8x8.
On it and finish it. Will be the topic for the competition
section "Etudes". Having reached this stage, I
decided to see how to make
printing 42 characters per line in
major programs and found a similar algorithm in the editor,
assembler XAS ((c) Max Petrov) and a text editor ZX / IBM
EDITOR ((c) Oleg Khokhlov). The desire to reinvent the wheel
lost, and lead fragments
others' programs do not consider it possible for ethical
reasons.
PROCEDURE FOR MULTIPLICATION HL = B * C.
(ZX REVIEW 96/4-5, p. 69).
Propose options for procedures,
which is long, but
runs faster when multiplied
large numbers (B> 15) and has no
zero-error syndrome.
The numbers in the comments mean: numerator - Length (bytes)
denominator - the time (cycles).
LD L, C; 1 / 4
LD D, B; 1 / 4
LD H, 0, 2 / 7
LD E, 0, 2 / 7
LD B, 8, 2 / 7
; --------; 8 / 29
;----------------------------
LOOP LD A, 1, 2 / 7
AND L; 1 / 4
JR Z, PASS; 2 / 7
ADD HL, DE; 1 / 11
PASS RR H; 2 / 8
RR L; 2 / 8
DJNZ LOOP; 2 / 13 8
; ---------; 12/472
Or (58 * 8 +8)
;-----------------------------
RET; 1 / 10
; ==============================
; TOTAL: 21/511
If the value of the register B of 1
15 procedure multiplication method of repeated addition (ZX
96/4-5, p. 69) is faster.
Algorithm for multiplication method
additions, with shifts in detail
described in the book of R. Tokheym "Fundamentals of Digital
Electronics, the world, 1988., P. 238-240.
Practical application protsedry multiplication may find
For example, when calculating the address of the start line
two-dimensional array.
CHANGES all sectors
Bootloader.
(OA Litvinov, ZX REVIEW 96/4-5,
p. 88).
Described a very annoying effect when using the 5
interpreter TR-DOS, which everyone knew, but did not speak. I
collided with him in 1994, when engaged in adapting a drive
accumulated tape versions. Did not pay special attention to
him, until by chance I saw when the cover is removed the
computer that this happens to the drive. Head begins to search
for unknown that, but judging by her behavior,
somewhere about 255 tracks. The head rests on the limiter, and
stepper motor hard trying to move it even further. So
You can align and shoot down. I struggled with this effect less
elegant and fast way, positioning the drive head to the zero
track before reading the next block. This eliminates a
consequence, but it would be know the reason.
Maybe someone from readers
found the cause of the violation of positioning? As I said,
This effect is manifested mainly when downloading programs that
are structured as follows: packed screen, then the main code
block. After unpacking the screen in 50% cases violation of
positioning.
And the use of loaders
using function 5 interpreter TR-DOS, with the union
blocks in a single file, it is most convenient for
programmers, thinking about the interests of users. Loader
the most compact and runs on
any version of the TR-DOS. Program
constructed in this way, you can always restore the fracture
directory. BASIC-part program is easy to find by bytes
# 80, # AA, and calculate the total number of sectors, looking
at boot disk using
Monitor type ADM, did not amount to
labor, even for beginners.
MINI-Driver Disk
(ZX REVIEW 95 / 4, p. 10).
This driver has one small drawback, leading to
great inconvenience to users. It works only with
drive "A", although more than half the users have to
At least two drives. If
with its use to create
procedure pending shipment to the disk state, which before
record will not issue warnings such as "INSERT DISK
INTO DRIVE 'A' ", and the user
decides to relax a bit and load the game with a drive "B",
leaving the system disk with the result of his work in the
drive "A", then his thoughts about the developer of such a disk
version is unlikely to can be expressed in the literary
language. Even if you find a place to post messages and force
the user to rearrange the drives look like it will be not very
professional.
In addition, the driver has a fairly long and requires
for their placement inseparable part in the memory. As a
result, it is easier to adapt the tape version program using
the functions 5 and 6 of the interpreter TRDOS. Yes, and it
will work on any drive in any version
TR-DOS.
READING TRACKS
(ZX REVIEW 95 / 4, p.56).
Correspondent mentions the protection of "MICROPROTECTOR",
use the command SH-93 "reading paths". If, in step through
Mikroprotektora see memory load address after its
implementation, notably the violation information. Therefore,
MICROPROTECTOR'e after reading track is used quite
long cycle of finding the correct sequence of bytes, located on
the white space at the end of track.
A program for reading FDU
track is also easy to detect
Misrepresentation 20-30
bytes after the start of field data.
Used directly, click "read track" is really difficult. The
book A. Larchenko and Rodionova "ZXSPECTRUM 'TR-DOS ...",
house" Piter ", 1994, str.209, written: "In view of certain
hardware features of Beta Disk'a execution of this command is a
loss of synchronization microcontroller.
Maybe somebody knows what
needs to be fixed in BETA DISK for
that did not happen out of sync?
ABOUT LIVE PROGRAMMING
KR1818VG93
(ZX REVIEW 95 / 2, p. 12)
Interesting idea about direct
Access to the registers by VG93
disable ROM. If it is necessary
for personal use, you can
just set the toggle switch that disables ROM. And about
VG93 was published enough to write at least potrekovaya
copyist, though The program of view and transfer files to
disks of different formats.
You can also disable selector addresses in the disk
interface. At the same time will have access to controller port
from any address in memory.
