A drop of solder - About the problem in the firmware of the extended keyboard (in the “Taganrog” scheme) in IS-DOS.

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(C) Ovsyannikov Andrey
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   ... About the problem in the extended firmware
keyboards (in the "Taganrog" scheme). Dry-
faith in iS-DOS to detect the fact of pressing
These keys use something like this
designs:

LD BC, #00FE
 IN A, (C)
 CPL
 AND #1F
 RET Z

   to which there will be an incorrect response, or rather,
no response. Below is a sign
addresses for some combinations with correct
by this bug:

 0 1 3 4 4 5 5 5 5 5 6 7 7 7 7
 X X X X X X X X X X X X X X X
 0 F 7 0 F 7 B D E F F 7 B D E
CS+1 FE FF FE FE FF FF FF FF FF FF FF FE FE FF FF
CS+2 FC FF FEFC FF FF FF FF FF FF FF FE FD FF FF
CS+3 FA FF FE FA FF FF FF FF FF FF FF FE FB FF FF
CS+4 F6 FF FE F6 FF FF FF FF FF FF FF FE F7 FF FF
CS+5 EE FF FE EE FF FF FF FF FF FF FF FE EF FF FF
CS+6 EE FF FE EE FF FF FF FF FF FF FF FE FF FF EF
CS+7 F6 FF FE F6 FF FF FF FF FF FF FF FE FF FF F7
CS+8 FA FF FE FA FF FF FF FF FF FF FF FE FF FF FB
CS+9 FC FF FE FC FF FF FF FF FF FF FF FE FF FF FD
CS+0 FE FF FE FE FF FF FF FF FF FF FF FE FF FF FE
CS+SSFC FD FE FC FD FD FD FD FD FD FF FF FF FF FF
CS+ENFE FF FE FE FF FF FF FF FF FF FE FE FF FF FF
CS+SPFE FF FE FE FF FF FF FF FF FE FF FE FF FF FF

SS+1 FC FD FF FC FF FF FF FF FF FD FF FF FE FF FF
SS+2 FD FD FF FD FF FF FF FF FF FD FF FF FD FF FF
SS+3 F9 FD FF F9 FF FF FF FF FF FD FF FF FB FF FF
SS+4 F5 FD FF F5 FF FF FF FF FF FD FF FF F7 FF FF
SS+5 ED FD FF ED FF FF FF FF FF FD FF FF EF FF FF
SS+8 F9 FD FF F9 FF FF FF FF FF FD FF FF FF FF FB
SS+9 FD FD FF FD FF FF FF FF FF FD FF FF FF FF FD
SS+0 FC FD FF FC FF FF FF FF FF FD FF FF FF FF FE
SS+P FC FD FF FC FF FF FF FF FF FD FF FF FF FE FF
SS+O FD FD FF FD FF FF FF FF FF FD FF FF FF FD FF
SS+ENFC FD FF FC FF FF FF FF FF FD FE FF FF FF FF
SS+L FD FD FF FD FF FF FF FF FF FD FD FF FF FF FF
SS+K F9 FD FF F9 FF FF FF FF FF FD FB FF FF FF FF
SS+J F5 FD FF F5 FF FF FF FF FF FD F7 FF FF FF FF
SS+SPFC FD FF FC FF FF FF FF FF FC FF FF FF FF FF
SS+M F9 FD FF F9 FF FF FF FF FF F9 FF FF FF FF FF
SS+N F5 FD FF F5 FF FF FF FF FF F5 FF FF FF FF FF
SS+B ED FD FF ED FF FF FF FF FF ED FF FF FF FF FF
SS+Z FD FD FF FD FF FF FF FF FF FD FF FD FF FF FF
SS+X F9 FD FF F9 FF FF FF FF FF FD FF F9 FF FF FF
SS+V ED FD FF ED FF FF FF FF FF FD FF F5 FF FF FF

   Вверху таблицы - адреса в ПЗУ, где нуж-
но прошить ячейку. Вместо X нужно  подста-
вить порядковый  номер  клавиши  от 0 до F
(для всех адресов в строке одинаковый).

   Что же касается увеличения числа клавиш
до 32,то можно сделать так:распаять допол-
нительные 561КП2 (можно "по-голубому",мас-
сы и сигналы со  счетчиков - вместе, входы
и  выходы - раздельно) и  573РФ2 (все ноги
вместе, кроме  тех, куда  приходят  выходы
561КП2). Подадим третьи ноги КП'шек каждая
на“our own” ROM, and we’ll let it go to the meters through
element LI.

 ┌────┐
 3rd leg KP2 ─┬──│ & │──── to 561IE10
 3rd leg KP2'─│┬─│ │
 ││ └────┘
 ││
 │└──────── to 20,573RF2'
 └───────── to 20,573RF2

  (I haven't done this yet, but it should work)

   I “dug up” another “bug” in the por-
that #7FFD  for reading ( newspaper WP#7, o DOS
v6.05 ). I analyzed the circuit and did
port decoder on 555LL1 (all signals
for sampling should be in "0"), did not
start a DOS signal (with it in TEST 4.30
port was not detected), but everything worked,
when on the 11th leg IR22 filed log."1".

   Now about the last "bizarre". InZX-GUIDE
#02 read articles about improving the screen and
suspension "SOUND" of the device. After acquiring
ability to think I thought:

   1. Responsible for displaying the picture/border
ULA multiplexers, but not a processor, but a re-
image/attribute gisters are read from memory
constantly. And why, with the standard
position (and resolution) of the screen, during
do not switch curbs and reverse
hardware screen (say, with #6000 ). When
In this case, it takes 32  cycles per line of the picture
(CPU/VIDEO/CPU/ATTR), for reverse - 24
(in a standard screen, the border area
starts with the address #4008  - this is how it is set
counters are added).

   2. Sound must be output with a strictly fixed
regulated address of this area (for each
channel, of coz, your address). At the same time, the hour
The sampling rate is constant - 15625 hertz,
and there is no pause in 36 μs (for a while
lines of pixels).

   3. Use this mode for output
tricolor pictures, rolling up what is chi-
disappears during the curb and reverse into
some 32 byte RAM (pair 155RU2)
and output along with the picture. Remember
you just need a string. At the same time, it is possible
still refuse attributes by scanning in
the time of their clock cycles is another memory area.

   4. Hang up all this “nonsense of the old
senility" to a certain port, and cut off all
this trouble by some kind of toggle switch.
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