SYSTEM
(C) Pavel Nikitin.
WORKING WITH TR-DOS in assembler
---------------------------
In this article we will discuss
some techniques use
functions of TR-DOS when programming in assembler.
1. FORMAT TRACK.
Many programmers consider
formatting operation Tracks
mystery. Between
to format the track in an arbitrary way is not so
difficult. Type the following program in any assembly, and
You'll find this:
ORG # EA60; Start address (60000 in decimal)
DI; Disable interrupt
LD A, # 8; Code Download command VG93
CALL ZAGR
LD A, # 3C; side code (equal # 3C and # 2C
; For acc. upper and lower sides)
LD C, # 00; track number (in this case, the 0th)
CALL SEARCH; Calling searching for tracks
CALL FORMAT; procedure call format
CALL FORMAT; (preferably to call several times)
EI; Interrupt Enable
RET; Back to BASIC
ZAGR LD IX, # 2FC3
JP TO_TRDS
SEARCH LD IX, # 2F4D; address in ROM TR-DOS
, Searching for tracks
TO_TRDS PUSH IX; pushes the address of procedure
JP # 3D2F; Go through the stack in ROM TR-DOS
FORMAT LD HL, FRM_DAT; sequence of procedures
LD BC, # 007F; directly
LD A, # F0; producing
LD IX, # 2F57; formatting
PUSH IX
LD IX, # 3FCA
PUSH IX
LD IX, # 2FC3
JP TO_TRDS
Do not forget that formatting procedure is nothing
otherwise, a record, but not the data (your programs, arrays,
and etc.), and bytes of system information on the sector.
FRM_DAT - a list of bytes describing the sector of
track.
FRM_DAT DEFS 50, # 4E; first gap.
DEFS 12, # 00
DEFS 03, # F5; recording three bytes # A1
, And initialize the checksum.
DEFB # FE; Address label index data,
, Ie # FE "speaks" SH, what's next
; Are traded (on the track, sectors, etc.)
; Data.
DEFB # NN; Track Number
DEFB # NN; Number of
DEFB # NN; Number sector
DEFB # NN; length of the sector (ranging
; 0,1,2,3 for acc. length in bytes
; 128,256,512,1024)
DEFB # F7; recording two byte checksum
DEFS 22, # 4E; second gap
DEFS 12, # 00
DEFS 03, # F5; Initializing checksum
DEFB # FB; (says "SH, that further written
; Data from which and are your files)
DEFS NNNN, # 00; data (the number depends on the # NNNN
; Sector size - respectively
, 128, 256, 512, 1024 bytes)
DEFB # F7; recording two byte checksum
DEFS 54, # 4E
For each track, you need to
make a number of tables FRM_DAT, how many
sectors you want to get in
this track:
SECTOR1_FRM_DAT 1
SECTOR2_FRM_DAT 2
etc.
But it must be remembered
that one track can be prescribed
approximately (16 * 256 128) bytes
information.
Next comes a list of basic
procedures ROM TR-DOS, used when formatting.
1) When you sign the register A should
contain a command code. Procedure
provides a check at the end
command and executes the delay.
# 2F57 OUT (# 1F), A; entry in the register commands
, And the number 8 from the battery
# 2F59 IN A, (# FF); check at the end of command
AND # 80
JR Z, # 2F59
PUSH BC; Saving BC
CALL # 3DFD; Call Subroutine Delay
POP BC; Recovery BC
RET; Return from procedure
2) are entered into the instruction register VG93
the number of battery
# 2FC3 OUT (# 1F), A
RET
3) Internal procedure
TR-DOS, performing a delay
# 3DFD LD A, # 50, two elementary
# 3DFF LD C, # FF; nested loop
# 3E01 DEC C; providing
JR NZ, # 3E01; delay
DEC A
JR NZ, # 3DFF
RET
4) When you sign the register A contains
number to boot the system
register. Register C contains a number of the first track file.
The procedure provides a recording of the track number in the
register data, executing the actuator drive to the right track,
check for the command and execution delays.
# 2F4D OUT (# FF), A; Load System Register
; Code of # 3C and # 2C
LD A, C; transfer of the register C to A
OUT (# 7F), A; Entering the track number in the
registration data
CALL # 3DFD; Call Subroutine Delay
LD A, 18
OUT (# 1F), A
# 2F59 IN A, (# FF); check at the end of command
AND # 80
JR Z, # 2F59
PUSH BC; Saving BC
CALL # 3DFD; Call Subroutine Delay
POP BC; Recovery BC
RET
5) The procedure, output from
information (write to disk).
# 3FCA IN A, (# FF); cycle expectations
AND # C0
JR Z, # 3FCA
RET M
OUTI; Listing Information
JR # 3FCA
Using the procedure described
formatting, you can put
"Tag" on the disk, if you format the track as follows: first 16
sector of the Standard, and one with
number n> 16 128 bytes.
When copying such a disc
Last track copyist
Sector will not notice and he will not be copied. Track can be
easily test the reading of his standard procedure TR-DOS:
LD B, 1; Number of readable sectors.
LD C, 5; code read command of sectors.
LD D, TREK; track number.
LD E, SECTOR; number of sectors.
LD HL, ADDR; Address accommodate the readout sector.
CALL # 3D13; Group entry procedures for TR-DOS.
RET
2. DRIVER read from disk, do NOT
Requires System Variables TR-DOS.
Many of the toys, especially multi-level, not always well
amenable diskovizatsii using the standard download procedure
TR-DOS, because at This should restore the system variables
TR-DOS, to allocate a buffer, etc.
Below is a sector driver read the disc, with skilful
the use of which load
the disc will be less
painful for the program, because
driver does not need the system variables and an additional
buffer for reading, and with no problemma
interrupts.
Parameters for input:
HL - the load address in memory;
DE - the initial track, the sector;
B - number of sectors.
LOADER DI; disable the interrupts.
NXTT PUSH BC; Saving BC.
PUSH DE; --//-- DE.
LD A, D; identify the physical
OR A; track number and the parties.
RRA
LD C, A
LD A, # 3C; # 3C - code of zero.
JR NC, SIDE; Go to the installation side.
LD A, # 2C; # 2C - code of the first part.
SIDE LD IX, # 2F4D; Calling the installation side.
CALL TO_TRDS
POP DE; Recovering DE.
POP BC; --//-- BC.
CONT PUSH BC
PUSH DE
LD IX, # 2F1B
CALL TO_TRDS; Just reading the sector.
POP DE
INC H
INC E
BIT 4, E; If the sector has passed for 15 th,
JR Z, NXTS; it becomes a 0-vym and track
LD E, # 00; incremented.
INC D
POP BC
DJNZ NXTT
RET
NXTS POP BC
DJNZ CONT
TO_TRDS PUSH IX; procedure call TR-DOS'a
JP # 3D2F
EXAMPLE:
LD HL, # 6000; Reading directory drive
LD DE, # 0000 at # 6000.
LD B, # 9
CALL LOADER
EI
RET
Using this driver, you must
remember that the reading errors with
disk are not processed. If
length of the feed unit is not
multiple of 256, then no special
measures will be teryatsya 1 <= n <= 255 bytes
information. Bytes nn = (256 * count
sectors - the length in bytes) will be
corrupted. They must be preserved
(Useful for multi-block
programs)
EXAMPLE: To be produced by loading # 2000 bytes at address #
6000 with preservation of "spoiling" bytes
in the display area.
LD HL, # 6000; Load address
PUSH HL
LD DE, # 2000; Number of bytes
ADD HL, DE
PUSH HL
PUSH DE
LD DE, 16384; Save
LD BC, 256; "spoiling"
LDIR; bytes
POP DE
LD A, D; Calculation
QR A; number
JR Z, M1; downloads
INC D; sectors
M1 LD B, D
POP DE
POP HL
PUSH DE
LD DE, START_TR_SEC
CALL LOADER; Calling bootloader
POP DE; Recovery
LD HL, 16384; spoiled
LDIR; bytes
EI
RET
You may ask how you can load levels from the disk, not
knowing their primary track and the sector? For
This should highlight the main
(Main) block, process it and
after written one after the other levels:
main block
level1
level2
level3
etc.
After this procedure, let
command MOVE, that the files are placed one after the other not
only in the catalog, and that between
they had no extraneous information. Make a table size (in
sectors) at all levels. After downloading main_blok record last
track / sector. Then, choosing the level, take from the table
length and add to the last track / sector, calculating initial
track / sector needs level.
This will help you next
procedure that the initial
track / sector returns track / sector
with a pass to # nn sectors.
DE - beg. track / sector.
A - number of skipped sectors.
According to the exit in DE new track / sector.
LD B, # 10; number of sectors per track.
ADD A, E; Skip to start of the track.
M1 CCF
SUB B; Move to the track.
JR C, M2; All?
INC D; No, to increase the track number.
JR M1
M2 ADD A, B
LD E, A; new start sector.
RET
3. FEATURES OF THE BUTTONS
MAGIC.
Another little thing that you
can be useful - is the protection
from MAGIC'a. Below, we consider
three elementary version of the defense.
a) Pressing MAGIC spoiled two cells, which are stored
survey data keyboard
(LAST_KEY). You will be able to without them
Labor test.
b) If you put a stack of screen
(SP <= # 4038), then when you save
register stack "climb" into the ROM and
in this work MAGIC'a end.
a) "RESET" VG93:
CALL RESET
EI
RET
RESET LD HL, # 1FF3
XOR A
PUSH HL
DI
JP # 3D2F
Use this technique should be after all the downloads, because
VG93 if not restore, then
read it will not.
P. Thanks in advance for all
additions and corrections. You
should be noted that this
article does not purport to be complete
coverage of the issues. If everything goes perfectly
plain and simple, you, dear readers, have forgotten how to think
and lose your cravings for comprehension
incomprehensible.
