Problem with SXSim

Valio

Can somebody plz explain me why SXSim doesnt
correctly initialyze constant's.


I took some code from included samples:

            ORG    $8

temp        DS    1            ;temporary workspace

            ORG    $10

acc0        DS    1            ;pwm accumulators
acc1        DS    1
acc2        DS    1
acc3        DS    1
acc4        DS    1
acc5        DS    1
acc6        DS    1
acc7        DS    1

duty0        DS    1            ;pwm duty cycles
duty1        DS    1
duty2        DS    1
duty3        DS    1
duty4        DS    1
duty5        DS    1
duty6        DS    1

The 0x and 1x row of reg file in simulator have
random garbage data instead initialized "1"
as it seen from code above.

So why study example doesnt work correctly ?


Thanks a lot.

Post Edited (Valio) : 6/4/2009 10:05:23 PM GMT

PJMonty

Valio,

You're not initializing those variables, just setting aside space. The "1" means "make this variable take up one byte of memory", not fill this variable with the number 1.

Thanks,
PeterM

Valio

I see Peter.

I thought vars could be initialized this way, not just reserving space

I took PWM.src example from "SX Assembly" directory of installation.
If it's so, means this code doesnt works, as far vars contain garbage?
Could you take a look plz.

All above means it not possible have pre-initialized variables and
they should be set by itself fro constant. How can I make org directive
refer to program space ?


Thanks,
Alex

Post Edited (Valio) : 6/5/2009 5:31:24 AM GMT

JonnyMac

Alex,

You're a bit too quick to say the program "doesn't work" -- it does; what it doesn't do is initialize the PWM settings. Random values in the duty* variables will be output to the port; the values in the acc* registers will be overwritten every time the interrupt runs so they're it doesn't matter that they're not initialized. If you look at the code you'll find this comment:

;Interrupt routine does all PWM work, however, duty0-duty7 values may
;be updated here to modify individual PWM pin duty cycles.

This is an invitation to set one or more of the duty* variables before running the loop (at Main). You can use mov for a non-zero value of clr if you want to set a duty cycle register to zero.

Zoot

e.g.

acc0        DS    1            ;pwm accumulators
acc1        DS    1
acc2        DS    1
acc3        DS    1
acc4        DS    1
acc5        DS    1
acc6        DS    1
acc7        DS    1

duty0        DS    1            ;pwm duty cycles
duty1        DS    1
duty2        DS    1
duty3        DS    1
duty4        DS    1
duty5        DS    1
duty6        DS    1
duty7        DS    1 ; to get a nice round half bank

; clear duty registers
CLR duty0
CLR duty1
CLR duty2
CLR duty3
CLR duty4
CLR duty5
CLR duty6
CLR duty7

; or loop it....
MOV W, #duty0
MOV FSR, W
:loopme
CLR IND
INC FSR
JNB FSR.3, :loopme

; looping with non-zero init value
MOV W, #duty0
MOV FSR, W
MOV W, #128 ' preload W with duty val
:loopme
MOV IND, W
INC FSR
JNB FSR.3, :loopme

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Post Edited (Zoot) : 6/6/2009 6:05:56 PM GMT