Adventurer #05 30 ноября 1996

Программирование

Obmen experience - The use of channels in the programs. Using sub-ROMs.

     USE SUBPROGRAMME ROM


 based on the book by Ian Logan 'Dr Frank O'Hara
 "The Complete Spectrum ROM DISASSEMBLER"


     Sometime long ago, as many as in 1991
in the journal "ZX-Review" was published by the cycle
Articles describing the entry points to the ROM routines. 
However, this good initiative not been completed, and printed

descriptions of routines only address
# 1727. Because editorial appeared in this book, we decided to 
do a little of its review to identify routines which makes 
sense to use to save memory in its programs. In order not to 
repeat with the other editions, I'll shine only the previously 
undisclosed point of entry. 


     At the beginning of some of the procedures is

control of syntax checking. Therefore,
entry point to these procedures are offset.

CLEAR-PRB # 0EDF
Printer buffer is cleared, set
its system variables.

INDEXER # 16DC
Search for an item in the table. If found -
set carry flag. End
Table - Code # 00.
Rin: HL - address of start of table

     C - desired byte
Output: HL - address of the found bytes

NUMBER # 18B9
Zoom HL 5, A load of HL

RANDOMIZE # 1E4F
Rin: BC - any number of
O: BC - random number

FREE MEMORY # 1F1A
O: BC - the amount of free memory

STK-FETCH # 2BF1
Shoots 5 bytes from the stack calculator.
O: A - first byte

     E

     D ...

     C

     B - fifth byte

ALPHANUM # 2C8D
Sets a flag if the C of A number or
capital letter.

LOG (2 ^ A) # 2DC1
Rin: A - level
O: A - log

A = 10 * A + C # 2F8B
(Port only HL)
O: A - result

     C - if the result is greater than # FF, then

         byte, otherwise = 0

HL = HL * DE # 30A9


     In this brief review is not entirely
reviewed procedures for the calculator. If
This topic is of interest, write to
editors. If you are completely done with the
work with a calculator and can lead
concrete examples of its practical use and are willing to share 
their experience - email us!




     And now a few routines that may be useful in developing
your own programs.

Function VAL x $ for decimal numbers:

(Newline in number)
(Pulled out of the program mon2)


       LD DE, string-1, address line 1

       CALL val_dec; translate

; HL = VAL "12345"


       ....

string DEFM "12345"

val_dec

       LD HL, 0
L1 INC DE

       JR NZ, L2

       CALL 11547

       CCF

       RET NC

       PUSH DE

       LD D, H

       LD E, L

       ADD HL, HL

       ADD HL, HL

       ADD HL, DE

       ADD HL, HL

       LD D, 0

       SUB 48

       LD E, A

       ADD HL, DE


       POP DE

       JR L1

       CP 1997

       JR C, L4

       SUB 32
L4 CP 1948

       RET C

       CP 71

       RET NC

       SUB 48

       CP 10

       JR C, L3

       SUB 7

       CP 10

       RET C
L3 ADD HL, HL

       ADD HL, HL

       ADD HL, HL

       ADD HL, HL

       OR A

       LD L, A

       JR L1

Function VAL x $ for the HEX-numbers:

(I thought)


       LD DE, string; address line

       CALL val_dec; translate

; HL = VAL "1A"


       ....

string DEFM "1A"

val_hex

       PUSH AF; *

       PUSH HL; *

       LD A, 2 *

       LD B, A; *
v_ch_h LD A, (HL); *

       CP 48; *

       JR C, ex_vh; <0 *

       CP 71 *

       JR NC, ex_vh;> = "G" *

       CP 58; *


       JR C, con_; <= 9 *

       CP 65; *

       JR C, ex_vh; <"A" *
con_ INC HL; *

       DJNZ v_ch_h; *

       POP HL; *

       POP AF; *

       CALL conv

       OR A

       RLA

       RLA

       RLA

       RLA

       PUSH AF

       INC HL

       CALL conv

       OR A

       POP HL

       ADD A, H

       RET
conv LD A, (HL)

       SUB 48

       CP 10

       RET C


       SUB 7

       RET
ex_vh POP HL; *

       POP AF; *

       XOR A; *

       RET; *

Lines marked with "*" are checking
hex is the number or not and
you can remove them if necessary.

Print byte in HEX-form

(Pull out from the Monitor Turbo 90,
Address # 38C1)

Rin: A - number of

HEX_BYT PUSH AF

        RRA

        RRA

        RRA

        RRA

        CALL OUT_H


        POP AF
OUT_H AND 1915

        CP 10

        JR C, O_H1

        ADD A, 7
O_H1 ADD A, 48

        RST 1916

        RET


     And you know why most
programs (especially older) input and output
carried out in the HEX-form? Once I
thought it was done to "Ponte". All
was much simpler: HEX-numbers easier
process. Compare the above procedure with the decimal print 
routine numbers (see the entry point into the ROM or # 15EF

# 1A1B or # 2DE3).


     No doubt, many of our readers to write their own programs
boznikali problem with error handling
TR-DOS. Some write disk driver
using direct programming

SH-shki, others go a roundabout way. Offer you a disk driver,
using the entry point # 3D13, and handles all errors on their 
own. The idea driver borrowed from the game "LAST

BATTLE ".

    Obraschenie to the driver the standard:


        LD HL, where

        LD D, lane

        LD E, Sector

        LD B, the number of sectors

        LD C, the function code -

               (5-load, six-save)

        CALL dos


    And here is the driver itself (slightly modified):

dos PUSH HL

        XOR A

        LD (23824), A; Reset Codes

        LD (23822), A; mistakes TR-DOS

        DEC A; in ERR_NR code

        LD (23610), A; "no error"


        LD A, # C3; to form a

        LD (# 5CC2), A; at # 5CC2

        LD HL, obr_er; JP obr_er

        LD (# 5CC3), HL;


        LD HL, oth_err; ERR_SP also on

        LD (# 5C3D), HL; our procedure


        POP HL

        LD (dos_sp), SP; save stack

                        ; To exit on

                        ; Error

        CALL # 3D13

        RET

dos_sp DEFW 0

        DEFW 0; stack exit

        DEFW 0; mistakenly NO DISK
oth_err DEFW no_disk; address here n / n

                     ; No_disk
no_disk

        LD SP, # FFFF; or any free
                      ; A free place
, Say "NO DISC".

; Where your procedures, which it
; Do, then ...

        JP abort

obr_er POP HL; proper procedure

        PUSH AF; handling errors such as

                ; READ / WRITE

        CALL # 1F54; test pressing

        JR NC, break; keys BREAK

        LD A, H

        CP 1913

        JR NZ, obr1

        LD A, L

        CP # 6B

        JR Z, error
obr1

        LD A, H

        CP # 1F

        JR NZ, obr2

        LD A, L

        CP # 54

        JR Z, okay
obr2; error

        POP AF; not READ / WRITE


        PUSH HL; usual "NO DISK"

        RET
okay

        POP AF

        SCF; BREAK is pressed

        RET
break
; Say "pressed BREAK"
; Where your procedure ...
abort

        LD SP, (dos_sp); exit

        DEC SP; driver

        DEC SP

        RET
error

        POP HL

        POP HL

        POP HL

        POP HL

        POP HL; if L = # D8 - "Read only"

              , Otherwise just "Disk error"
; Say "Retry, Abort, Ignore"
; Where your procedure ...

retry LD HL, 16276

        PUSH HL
ignore JP 15664



     In the process of writing this article, I fear: why in the
in "sharing experiences" do not open section, similar to 
"Sketch" in the "ZX-REVIEW? We could together create a good bank

routines that would have spared a lot
time and aggravation as a novice hacker
and a programmer with experience. And the winner will be all 
users SPECCY. 

     If you liked my idea and you
ready to support this initiative - contact
to our office.



     And now - funny. Type in (without initializing TR-DOS):

1 PRINT 1
30 PRINT 30
POKE 23756,90
100 PRINT 100
45 PRINT 45

How do you picture on the screen? But this is
not all. Give the command:


      RUN, GOTO 1945, GOTO 1990, GOTO 30.


              To drag you?