Info Guide #02

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Assembler - A short lesson in assembler for lamer (continued)

       Lesson assembler lamer.

            (Continued)


   Today I'm going to tell you about
methods of interrogation keyboard interrupt, and
also try to fix their mistakes, which made the previous issue.


          1. I'll start with the error.


   The last time I was so scared uploaded
a description of the assembler directives, and
very incomplete and misleading description. But
if you read carefully the text of ALASM,
it is more likely to have missed this nonsense by
ushey.Dalneyshee refers to those others who
believe this delirious and did not read opisaniya.Vo
avoid.

   We can not say that the directive does not take place in 
pamyati.Vzyat least DEFB (DB): She, of course, not a command 
processor, but the memory of eating honest: as much as bytes of 
information after it zapisano.Ili another directive: 

     DUP 8

     RR C

     RLA

     EDUP

   After compiling this piece will look like this:

     RR C

     RLA

     RR C

     RLA

     RR C

     RLA

     RR C

     RLA

     RR C

     RLA

     RR C

     RLA

     RR C

     RLA

     RR C

     RLA

   Moreover, it takes more memory than

     RR C

     RLA

   After all, while all of this memory is populated entirely 
processor commands! 

   About the directive ENT I wrote a full
erundu.Skazhu honest: it's because I was
yet once it does not really ispolzoval.Na this directive goes 
in tandem with DISP and the lower limit a piece that DISP top 
ascribed to work in other address (es not to the address on 
which this piece compiled). Example:


     ORG # 6000

     LD HL, KUSOK

     LD DE, # 4000

     PUSH DE

     LD BC, KUSEND-KUSOK

     LDIR

     RET
KUSOK DISP # 4000


  <Kind of a program

   completely stuffed

    CALL, JP, etc., and

  because conflicts between>


     ENT
KUSEND

   By the way, if you tag KUSOK KUSEND and insert inside a 
block DISP-ENT, these tags just like everyone else in this 
block, will be recalculated and, naturally, will not contain 
those values ​​which we would wanted.


   The directive ORG is permissible two parameters, and if the 
two of them, then the second - is the number of pages, where we 
compile. And the program is run, incidentally, is not the first 
ORG, and the last! 

   Directive INCLUDE <name> []
used to load modules for the long
programs. When compiling an assembler, stumbling on this 
directive loads the appropriate file (if it's not in memory) 
compiles it, and then continues compile the main program to the 
point where it was interrupted. 

   Directive INCBIN <name> []
loads the code file (by the way, you can ukazyat extension 
through the point) on the current at compile time, and moves 
this address compiled at the end of this file.



         2. Poll keyboard.


   The keyboard of the old ZX Spectrum 48k klavish.Ostalnye 
contained 40 key enhanced keyboard are a combination of both, 
For example BREAK = CAPS / SPACE, EXTEND = CAPS / SYMBOL, TRUE 
VIDEO = CAPS / 3, etc. 

   40 keys are collected at 8 poluryadov 5
keys in each:

# F7FE: January 2 3 4 5 # EFFE: 6 7 8 9 0
# FBFE: Q W E R T # DFFE: Y U I O P
# FDFE: A S D F G # BFFE: H J K L Enter
# FEFE: CapsZ X C V # 7FFE: B N MSymSpace


   After a while I explain what it is
for the number on the left, but first tell you about
how the processor works with peripheral devices (ie, generally 
with all devices except memory). ____ 

   Devices are selected IORQ = 0 (ie
When this signal is active). Then the device v_kotorye record 
must verify that WR = 0 (t.e.aktiven recorded signal) and 
device iz_kotoryh receive data, check that RD = 0 (active 
signal reading), and afterwards, all devices are checked 
certain combination of address signals, which have each device 
has its own. For example, the beeper (BEEPER) is selected when 
A0 = 0. 

   Where are these signals? Naturally
from the processor. Combination

   ____ __

   IORQ = 0, WR = 0

produced by teams OUT, and kombinatsiya____ __

   IORQ = 0, RD = 0

- When teams IN.

   Like, we are on these teams have not talked about. So:

   OUT (), A - burn the battery in the
port, whose address is: A (Senior
B) * 256 +  (Low byte). Contents
the battery is displayed on the data bus. Port address, of 
course, is displayed on the bus address.


   OUT (C), <register> - write register in
port, whose address is contained in the register pair BC. 
Register can be: A, B, C, D, E, H, L.


   OUT (C), 0 - to record a zero in the port BC.Komanda 
undocumented, many assemblers are not supported. On the 
processor Z180 resets.


   IN A, () - read data from port
in the battery. Port Address = A * 256 + .

   IN <register>, (C) - to consider a case
data from the port of BC.

   IN F, (C) - read data from the port of BC
without remembering. Instead, appropriately set the bits of the 
flag register. (In what way they are set, not znayu.U Larchenko 
and Rodionov not specified.) Team undocumented.

In some assemblers, it is written
as IN (HL), (C).

   Teams IN r, (C) and OUT (C), r are called
appeal to the port with complete addressing, in
Unlike incomplete address OUT (b), A. Ko
many ports (including a musical
coprocessor AY) can only be accessed with
fully addressed.

   There are also commands to access block portam.Mne somehow 
did not have to use them.


   Those mysterious numbers that I cited
against the names of the keys to poluryadah are just addresses 
relevant portov.A read from these ports are the following: 

  bit 7 - not defined;

  Bit 6 - reading from the tape. In many
computers is not implemented. In some
it is implemented so that there is read
random values ​​(due to the fact that I forgot
mask this bit of AND, in the first issue terribly sausage 
arrow); 

  bit 5 - not defined;

  Bits 4-0 - key state poluryada.
If a key is pressed, read 0, and otherwise - 1.Bolee lower bits 
are more extreme keys. 

   Example of use:
START CALL <routine>

     LD A, 239; byte poluryada 6-0

     IN A, (254), reads data

     RRA; 0-th bit goes into CY

     JR C, START; cool, until they click 0

   In fact, every keyboard port
chosen for two thrown down bits: bit 0
and even to some in the range of 8 to 15.Esli
to lose a few bits, will choose
Several poluryadov, and their contents
will overlap by AND. Example:
LOOP XOR A; all bits cleared

     IN A, (254); polls all poluryady

     CPL; almost equivalent to a combination of:

     AND 31; AND 31: CP 31, but shorter

     JR Z, LOOP; until they click ANY KEY

   Another method is to survey key
the use of sub-ROMs and the results of interruption of IM 
1.Naprimer, the procedure for 8020 resets CY, if pressed BREAK. 
And working with an IM can be as follows: 

     RES 5, (IY +1); reset flag "ANY KEY"
NOKEY HALT; if you remove HALT, can stock
     BIT 5, (IY +1); Snooty on the neck. com!

     JR Z, NOKEY; until they click something

     LD A, (23560); sist.peremennaya LAST_K

   As a result, the battery will be code
the last key pressed. Be careful: If you set CapsLock, then you
will be read out completely big letters! A set CapsLock can be 
as follows: 

     LD (IY +48), 8; sist.peremennaya FLAGS2

   In his AC Edit I successfully combine
both ways of polling keys.


      3. Some of the other ports.


  The same port (254), is selected to record
responsible for the color change curb, squeaker and output to 
tape. Bits of it are: 

  Bits 7-5 - not used;

  Bit 4 - state pischalki.Chtoby cause
sound, you need to constantly switch on
bits;

  Bit 3 - output to tape;

  Bits 2-0 - Color bordyura.U curb may
be 8 different colors. Brightness in these
colors otklyuchena.Chtoby get on the curb
static images, you need every time from the beginning of human 
interruption in some way to change this color, while the 
electronic beam draws the screen.


   Example:

     XOR A; black

     OUT (254), A; border turns black


  Port 31 (# 1F) to read the story about
state Kempston joystick:

  Bits 7-5 - is always equal to 0 if the joystick
connected, and otherwise on their status can not say anything 
definite; 

  Bit 4 - fire (1 - pressed, 0 - released);

  Bit 3 - down (similar);

  Bit 2 - up;

  bit 1 - right;

  Bit 0 - left.


  Port 32765 (# 7FFD) - Expansion Port
memory (on record). Impossible to read
(In addition to several pathologists). Appointment
bits:

  Bits 7-6 - on the 128k not being used;

  Bit 5 - snap the port # 7FFD. If this
bit is set, the computer becomes forty
eighth with all the ensuing posledstviyami.Posle reset 
everything back to normal; 

  Bit 4 - If 0, the address will stick 0-16383 128-e 
PZU.Obychno do not need it, and this bit is set to 1, whereas 
in the lower addresses will have 48 e-ROM; 

  bit 3 - the number of the screen: if 0 - then the usual 
"first" screen 16384-23295 of page number 5, otherwise - 
"second" screen from the pages of Number 7;


  Bits 2-0 - number of pages of memory to be placed in the 
region 49152-65535. Here you need more detail.


   All at 128k, you guessed it, 8
pages of memory to 16k. From 16384 to 32767
always page number 5, from 32768 to
49,151 - Page number 2, but the above - has any, what you like 
(including 2 or 5). Upon leaving the assembly is installed

Account number 0, the assembler itself in number 4, the monitor
in the number 7, and the text of your program is likely to 
number 6. Page № 3 assembler uses a table of labels. So: 

   If you're not going to use the monitor, feel free to be 
overwritten by page number 3 and number 7. (Just do not 
Assemble at number 3 and number 7 with # C000 on # C8FF, since 
it is used as buffer at podgruzku Disk.) Pages number number

0, 1, unconditionally free. And if you become
really quite closely, you can overwrite and assembler with 
sources (respectively number number 4, 6). ,


   There are, of course, Spectrum'y and with great
memory (up to 2 Mb), but distributed
they are small. So what to write for them is not worth
the more so still you can not fully use all the features of 
extended memory, not having any. 

   Due to the large number and variety of pathologists with 
different versions of the decryption port # 7FFD, there was a 
so-called problem of port # FD.Nazvanie it due to the fact that 
computers "Pentagon-128" decoding port extended memory is only 
2 bits: A1 and A15, as a result of this port was made possible 
refer to incomplete address: 

     LD A, 23, 7-I Page

     OUT (# FD), A; write its number in the port

   You will not find it more convenient than

     LD A, 23

     LD BC, 32765

     OUT (C), A

   That's how many, and thought, and in many
programs (eg, by CodeBusters) is
it is part addressing the port. Of course, on some computers, 
such programs do not work. For example, the above example of 
the "Scorpio" will perceive as appealing to the port # 1FFD, 
and this is, of course, quite a different port (switching TURBO,

inclusion in the region 0-16383 page shadow RAM № 8, shifting 
shadow pages RAM, ROM, and still do not know why).


   I believe (and many others also think so) that all Spectrum 
equal, and if program does not work in some places because of 
that trifles as incomplete decoding ports,

this is a bad program. Of course, some
things, such as digital music with high
quality can be realized only in certain types of Spectrum 
("Pentagon", KAY, ATM, etc.), but that's another problem.

It let you Uncle Zonov explains why in
its computer processor brake
general field pamyati.A speaking on joint account, if the only 
support "Pentagon" (I say this despite the fact that I myself 
"Pentagon"), then sinkleristy who use other types of Spectrum 
(and their not less than 40%) could be seriously offended and

withdraw from the Spectrum. Good for us from this be? That's 
it. Incidentally, even the demo now working on "Scorpio". Learn!



  Ports 65533 (# FFFD), 49149 (# BFFD) are responsible for 
access to music coprocessor AY.U coprocessor 16 registers for 
different purposes. In order to write something any of them, 
you need to send its number to port 65533, and then data to 
this register, go down to the port 49149.Esli should, 
conversely, to read the data, then after recording the number 
in the register of port 65533 to read data from the same port 
65533. All analyzers, the volume in all sorts of boot '

oh it was based on the reading of the AY. The appointment of 
separate registers: 

  Number number 0, 1 - contains 12-bit period
(Not the frequency, namely, period!) Notes in channel A. And 
register 1 - Senior; 

  Number number 2, 3 - the period of the channel B;

  Number number 4, 5 - the period of the channel C;

  № 6 - Five digit period of noise;

  № 7 - Sound Control:

     Bits 6,7 - indicate the direction of exchange on the 
parallel port, and therefore we not interested;


     Bits 3-5 - if 1, then allowed the conclusion
noise, respectively, in channel A, B, C;

     Bits 0-2 - if 1, then allowed the conclusion
Notes to the channel A, B, C. But instead, if you manipulate 
the volume in the corresponding channel, we can get digital 
music! A If the envelope is included, then it will sound by 
itself! 

  № 8 - 4-bit channel volume A. Note that the scale of loudness 
is not linear, but rather, logarifmicheskaya.Esli set 4-th

bits of this register, then the volume will not be, and instead 
of coming on the envelope; 

  № № 9,10 - and similarly for channels B, C;

  № № 11,12 - the period of the envelope. When playing audio on 
the envelope used only the lower byte (№ 11);


  № 13 - 4-bit form of the envelope:

      0 - fade to zero;

     12 - sawtooth sound;

     13 - smooth increase to a maximum;

     14 - zigzag sound an octave
lower than 12;

  № № 14,15 - used for the exchange of
parallel ports.

   Of course, it is unlikely you'll play themselves
music through a direct appeal to AY, so that
As an example, show just how off the sound:

     LD DE, # E00

     LD C, # FD
OFF0 LD B, # FF

     DEC D

     OUT (C), D; select number register

     LD B, # BF

     OUT (C), E; writes a zero

     JR NZ, OFF0; and so on until the 0-th register


           4. Interrupts.


   Every 20 milliseconds (1 / 50 seconds) to
CPU staff come preryvaniya.Eto
reflected in the fact that, at the foot INT served
negative pulse. Pulse length, as
usual, each has its own pathologist, but do not talk about it.

   If, during the pulse were
enabled interrupt (command EI, off they command DI), then, 
depending the current mode interrupts, the processor

will perform the following:

   a) (IM mode 0) command, which came
with the data bus (not used);

   b) (IM mode 1) subroutine RST 56;

   c) (IM 2 mode) subroutine, the address which he read from a 
cell with address: I * 256 + , where I - register 
interrupt vectors. 

   In any case, before entering the interrupt routine the 
processor disables interrupts. 

   At the moment we are most interested in regime IM 2, t.k.v 
this mode, you can insert your own handler. 

   Since the state of the data bus is not defined in the 
general case (ie, not at all computer read out stably

255), it is desirable that the address of the handler
not dependent on the state of the data bus:). This
achieved a uniform filling of the same numbers of so-called 
interrupt table, length 257 bytes (for each of the 256 possible 
states of the SM from the table is read the same two bytes). 
Moreover, this table should be placed in the so-called fast 
memory (page number 0 or number 2), and some pathologists may 
podvisnut ... Example:

MUZ EQU # C000

     ORG MUZ
+ INCBIN "MUSIC"

     ORG # 6000

     DI

     CALL MUZ; initialize music

     LD HL, # FE00

     LD A, H

     LD I, A; I = # FE

     LD DE, # FE01

     LD BC, # 100

     LD (HL), # 5C

     LDIR; fill in the interrupt table

     LD L, (HL)

     LD H, L; HL = # 5C5C

     LD (HL), 195; JP

     INC HL

     LD (HL), IMER

     INC HL

     LD (HL), 'IMER

     IM 2

     EI


   <More program

    will work

     the music>


     IM 1; turn off IM 2

     JP MUZ; turning off the music and leave

IMER PUSH AF

     PUSH BC

     PUSH DE

     PUSH HL

     PUSH IX

     PUSH IY

     CALL MUZ +5; call music

     POP IY

     POP IX

     POP HL

     POP DE

     POP BC

     POP AF

     EI

     RET

   That is, if you hang on to interrupt any action (such as 
playing music), the program no longer has to be

this is followed, and we get a
kind of multitasking (many, but not two-,
because nothing prevents us to hang on
interruption of several different tasks, such as music and 
multicolor). 

   With enabled interrupt can not be included in TR-DOS, except 
at the first call TR-DOS interrupt disappears and in its place

will BASIC.I when returning from interrupt we get a little bit 
the wrong way:). Way to get around this, given in the book 
"TR-DOS for users and programmers. "In fact, this is not 
nuzhno.Prosto disables interrupts at the entrance to TR-DOS. 

   If you do not have enough space under the table break, put 
it in slow memory, For example, at # 5B00.No note that if your 
program will not work vezde.Esli and slow is not enough memory, 
you can leave the table only 2 bytes of at I * 256 255 (as done 
in TLW2). This you have greatly reduces the number of its 
polzovateley.Samy latest version: I = 59. Then the table (the 
length of 257 bytes to 48k, or 2 bytes to 128k) will be in ROM, 
and the procedure interrupt handling - at 65535.Postavte there 
JR, and at 65,524 (to indicates JR) put the handler. Now

performance of your program, in addition to
computer model, is limited more and version
Rom ...


          5. Useful tips.


   It is best to start typing program
with the lines:

     ORG # 6000

     LD (QUIT +1), SP

QUIT LD SP, 0

     LD IY, 23610

     IM 1

     LD HL, 10072

     EXX

     EI

     RET
END

   Who knows what registers can ruin your program while it's 
still buggy? A END tag allows you to always know the length of 
the programmy.Dlya after assembly in command mode, type: COUNT 
END-# 6000 

   The Council is also put into the program subroutine print 
16-digit numbers and call her from time to time in the main 
loop program. This will allow you to control the crash. 
Subroutine sm.v Section "Etudes". 

   Write a program beautiful and convenient for
ispravleniya.Chasche use CALL.Vydelyayte complete functional 
block in the subroutine, even if it is invoked only a 
raz.Sohranyayte registers podprogrammah.Ne think about shifting 
ability, use instead of JP JR. 

   All address tables, music, sprites, etc.
record in EQU.Eto allows you to easily change these addresses, 
if that. Recent experiments have shown that even numbers are 
used memory pages can change, and they, too,

must enter in EQU.

   When your program exceeds 4k (as in
I have 3 such programs), the text will not be placed in the 
16k-buffer. Have to select a module and load it on the 
directive: 

     INCLUDE "MYUNIT", a

   It will be loaded into another page and this will allow you 
to simultaneously edit both teksta.Dlya module should be 
selected routines that you do not have to fix a long time (I 
call their "immortal").


   Loads INCBIN'om data pages except that only during 
otladki.Luchshe just load them directly onto

tail of the program, and then flip LDIR'om. Then the program 
will be easier to ship in compiled form and zapakovat.Stoit to 
say that prog, scattered the page, to pack at all in any

packer can not?


          To be continued ...