Print Page - timer in CP/M+

Title: timer in CP/M+
Post by: litwr on 14:29, 01 January 16

I'm trying to find a way to use timer under CP/M+. I've made the code which calls firmware (KL_TIME_PLEASE) but it doesn't work. :(

Code Select


org &100
kl_time_please equ &bd0d
;; get address of routine to call to execute a firmware function
  ld hl,(1)
  ld de,&57
  add hl,de
  ld (firm_jump+1),hl
loop
  call firm_jump
  dw kl_time_please
  call PR00000    ;prints HL as decimal

;; make the end of line
  ld de,eol
  ld c,9
  call 5
  ld hl,cnt
  dec (hl)
  jr nz,loop

;; quit back to command-line
  ret

eol db 13,10,"$"
cnt db 20

;; execute a firmware function
firm_jump
  jp 0

PR00000 proc
        local PRD,PR0
        ld de,-10000
	CALL PR0
        ld de,-1000
	CALL PR0
	ld de,-100
	CALL PR0
	ld de,-10
	CALL PR0
	ld A,L
PRD	add a,$30
        ld e,a
        ld c,2
        jp 5   ;bdos

PR0	ld A,$FF
	ld B,H
	ld C,L
	inc A
	add HL,DE
	jr C,$-4

	ld H,B
	ld L,C
	JR PRD
        endp

What is wrong? Or is there any other way to get timer data with Amstrad CPC6128 CP/M+ ? A lot of thanks for any help.

Title: Re: timer in CP/M+
Post by: AMSDOS on 23:46, 01 January 16

Quote from: litwr on 14:29, 01 January 16
I'm trying to find a way to use timer under CP/M+. I've made the code which calls firmware (KL_TIME_PLEASE) but it doesn't work. :(
Code Select Expand
org &100 kl_time_please equ &bd0d ;; get address of routine to call to execute a firmware function ld hl,(1) ld de,&57 add hl,de ld (firm_jump+1),hl loop call firm_jump dw kl_time_please call PR00000 ;prints HL as decimal ;; make the end of line ld de,eol ld c,9 call 5 ld hl,cnt dec (hl) jr nz,loop ;; quit back to command-line ret eol db 13,10,"$" cnt db 20 ;; execute a firmware function firm_jump jp 0 PR00000 proc local PRD,PR0 ld de,-10000 CALL PR0 ld de,-1000 CALL PR0 ld de,-100 CALL PR0 ld de,-10 CALL PR0 ld A,L PRD add a,$30 ld e,a ld c,2 jp 5 ;bdos PR0 ld A,$FF ld B,H ld C,L inc A add HL,DE jr C,$-4 ld H,B ld L,C JR PRD endp
What is wrong? Or is there any other way to get timer data with Amstrad CPC6128 CP/M+ ? A lot of thanks for any help.

I had a good look at this, and even use a different routine for printing the number (which was published in AA54), but had no luck with it. The Winape Assembler had a problem with this statement:

Code Select

jr c,$-4

in the PR0 routine, so I replaced it with jr c,pr0 which I'm presuming was my mistake, though the Assembler was telling me that &-4 was outside it's range ("&" is used instead of "$"), perhaps this line is doing something in your assembler that it's not meant to, though I'm only guessing now, everything else looks fine to me, though it's obviously not giving you the result you want.

Title: Re: timer in CP/M+
Post by: Executioner on 00:22, 02 January 16

The WinAPE assembler shouldn't have a problem with jr c,$-4. I've just tested and it all seems fine and outputs FA as the relative address. $ is the current code location, so $-4 is the current code location minus 4. &-4 is the location #FFFC which would be outside the relative jump range of course.

Title: Re: timer in CP/M+
Post by: FloppySoftware on 00:44, 02 January 16

I have translated the source code to ZSM and assembled with it.

When I execute the COM file, WinAPE hangs.

I don't know what's the problem (yet).

Edit: The following code compiled with MESCC runs perfectly under WinAPE:

Code Select

#include <mescc.h>
#include <printf.h>
main()
{
    patch();
    printf("HL = %04x\n", get_time());
}
#asm
patch
 ld hl,(1)
 ld de,057h
 add hl,de
 ld (firm_jump + 1),hl
 ret
get_time
 call firm_jump
 defw 0bd0dh
 ret
firm_jump
 jp 0
#endasm

I think the problem is in the output subroutine.

Title: Re: timer in CP/M+
Post by: AMSDOS on 00:56, 02 January 16

Quote from: Executioner on 00:22, 02 January 16
The WinAPE assembler shouldn't have a problem with jr c,$-4. I've just tested and it all seems fine and outputs FA as the relative address. $ is the current code location, so $-4 is the current code location minus 4. &-4 is the location #FFFC which would be outside the relative jump range of course.

Well the problem was occurring when I converted the "$" sign to "&". Perhaps the fault lies in what that means?
I haven't seen an assembler use "$" to represent a Hexadecimal number, but I guess it's possible.

Title: Re: timer in CP/M+
Post by: Executioner on 04:56, 02 January 16

Quote from: AMSDOS on 00:56, 02 January 16
I haven't seen an assembler use "$" to represent a Hexadecimal number, but I guess it's possible.

$ is used to represent the current code location. For example,

org #1234

dw $

will generate the address #1234

org #1234

dw $ - 4

will generate the address #1230

Title: Re: timer in CP/M+
Post by: litwr on 06:54, 02 January 16

I am terribly sorry for my stupid question. :( The problem is very easy to solve. I forgot to save HL before BDOS call. So

Code Select

JP 5
in PR00000 should be replaced by

Code Select


push HL
call 5
pop HL

I was sure that BDOS (like AMSDOS, IBM PC DOS/BIOS, ...) preserves CPU registers. Thanks for the help anyway. The $-sign means the current code location and it also starts the hexadecimal number in pasmo-cross-assembler.

Title: Re: timer in CP/M+
Post by: FloppySoftware on 12:13, 02 January 16

Ooops! :doh:

Funny bugs (that we all do sometimes) :laugh:

CPCWiki forum

General Category => Programming => Topic started by: litwr on 14:29, 01 January 16