Problem with Test instruction used to ina

Christof Eb.

Hello,
during some experiments with adc, I tried:
test ina,inpin wz

to find the value of a certain pin and influence the zero flag. The code did not work.
Then I used:
mov help,ina 'read the input bit
test help,inpin wz

An this works.
What is the reason?
Christof

Mike Green

Chip discussed the use of certain special registers (like ina) in another thread. Basically, these must be used only in the source field of an instruction. If you use them in the destination field, you actually access the "shadow" memory location rather than the special register. This is true of all the read-only special registers like ina, cnt, par, etc.

Christof Eb.

Thanks, Mike, I will try to find Chip's thread about it.
And I tried:
test inpin,ina wz
which works.(!!)
Christof

cgracey

Also, the PHSA and PHSB registers must be read as source registers, otherwise you'll read back the value that you last wrote to them.

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Chip Gracey
Parallax, Inc.

Paul Baker

Yup, I made that mistake a few days ago, I figured since you could read and write to PHSA/B you could do wrlong phsa, hubmemory; but that doesn't work, it just kept writing -4 to main memory which was my initialization value.

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Paul Baker
Propeller Applications Engineer

Parallax, Inc.

Christof Eb.

Hello parallax-people

I think, it would be good, to get a warning from the assembler!!

Can you implement that?

Christof