This code needs a delay, but I do not know where the delay needs to go.
I have some delay code that is CPU independent.
unfortunately, there is no good way to relinquish processor time in 16-bit code
at least, not that i recall
you might look in the 16-bit section of the old forum for related posts by MichaelW, qWord, or FORTRANS
there is an INT that is supposed to work, but i didn't have any luck with it
it might be possible to thunk out to a 32-bit Sleep routine
or - maybe - there is some way to revector the keyboard INT 16h to make it work :redface:
Quote from: Magnum on January 08, 2015, 07:21:05 PM
This code needs a delay, but I do not know where the delay needs to go.
Quote from: dedndave on January 08, 2015, 10:38:13 PM
unfortunately, there is no good way to relinquish processor time in 16-bit code
at least, not that i recall
you might look in the 16-bit section of the old forum for related posts by MichaelW, qWord, or FORTRANS
there is an INT that is supposed to work, but i didn't have any luck with it
Hi,
There is a difference between releasing CPU control to Windows
and a delay. To relinquish processor time, see comments made by
a whole bunch of people when I was discussing my Viscalc program
in around April 2013. Dave had complained about 100% CPU usage,
and some "fixes" were suggested.
A simple delay routine will look at the clock tick values at 40:6C
maintained by the BIOS. A short delay, as below, simply looks for
a change. Count a number of ticks for a longer delay.
IF Delay
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
; Implies 200LX (or Windows 2k+) and no INT 15 delay routine,
; so we will use something similar to MsDelay from the PAL library.
; 15 November 2000 variable delay.
; 7 January 2001 used fixed medium delay (later chopped to min.).
DELAYER:
PUSH ES ; ???
PUSH AX ; After all this is a delay routine
PUSH BX
PUSH CX
PUSH DX
PUSH DS ; Save DS and point to BIOS data area
MOV AX,40H ; SEG BIOSSEG
MOV DS,AX
MOV AX,DS:[6CH] ; ClockTic
MOV DX,AX ; Save low word start time in DX
DLR_1:
MOV AX,DS:[6CH]
CMP AX,DX
JE DLR_1 ; Greater than Start?
POP DS ; exit processing
POP DX
POP CX
POP BX
POP AX
POP ES
RET
ENDIF
; - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Since I save all used registers, it should be safe to put a call to
it in any convenient place. Usually at the top or bottom of a
major routine.
Regards,
Steve N.
Steve,
your code is good. I had forgotten the topic. I think it's not necessary to save es on entry, because that holds only a pointer to the environment (we're speaking about a native DOS application). But pushing it makes no harm.
Gunther
Quote from: Gunther on January 09, 2015, 01:17:51 AM
Steve,
your code is good. I had forgotten the topic. I think it's not necessary to save es on entry, because that holds only a pointer to the environment (we're speaking about a native DOS application). But pushing it makes no harm.
Hi Gunther,
Thanks. Right ES is not used in that version and need not be
saved. Note the ??? in the comment there. In an earlier version
I mentioned, it was more complex to cause a longer delay and I
used LES to load the tick count to ES:AX.
DLR_1:
STI ; 4 Sep 03
HLT ; 4 Sep 03
LES AX,DS:[ClockTic] ; Get timer 55 ms tick count
CMP AX,DX
JE DLR_1 ; Greater than Start?
CMP AX,BX
JE DLR_1 ; Greater than Start+1? It also had a HLT for power saving for the HP 200LX MS-DOS
palmtop computer. (Which doesn't work with a Windows NTVDM.)
So I saved ES in that version. So it was "used", but as it turned
out, never usefully. So LES and HLT were dropped in the newer
version, and I thought about not saving ES, but not hard enough
apparently.
As an aside to Dave, to reduce CPU usage, I ended up using the
DOS keyboard functions rather than the BIOS keyboard functions.
Using the BIOS routines was simpler, but did not give control to the
Windows NTVDM to save CPU cycles.
Cheers,
Steve N.
; Bios clock has a pulse rate of 18.2 times/second
; 18.2 x 5 seconds = 91 Useful for delays UNDER 14 seconds.
; .5 second = 9.1 pulses
; .1 second = 1.8
; .05 second = 1
;
; The lowest two bytes can time up to 59 mins 59 secs.
.model small
.stack 200h ; 512 byte stack
.data
string db 'Timer tick tocking...','$'
.code
start:
mov ax,@data
mov ds,ax
lea dx,string
mov ah,9
int 21h
mov ah,0 ; function no. for read
int 1ah ; get the time of day count
add dx,9 ; add « second delay to low word 18 = 1 second
mov bx,dx ; store end of delay value in bx
again:
int 1ah
cmp dx,bx
jne again
exit:
mov ax,4c00h
int 21h
end start
What kind of data is ClockTic ?
I tried byte and word.
if it's the RDTSC clock, it would be a QWORD
the old DOS tick was 3 bytes i think - usually stored as a DWORD
For a short delay, with a potential resolution of 15.9 microseconds, you can count memory refresh toggles. Some BIOS code uses this method (or at least at one time did), see this post (http://www.masmforum.com/board/index.php?topic=13009.msg100785#msg100785).
But these days, at least on a system with a constant clock speed, RDTSC in a delay loop would probably be a better choice, but you need to know the clock speed to know the length of the delay (and on such a system this is fairly easy to do, at least approximately).
Thanks.
Was your delay code for 55 milliseconds ?
Quote from: Magnum on January 16, 2015, 01:25:15 PM
Thanks.
Was your delay code for 55 milliseconds ?
For my code, on call the delay is the number of milliseconds in AX.