Simple Assembly

Pliers · 2010-09-30 06:28

I'm learning assembly, I think.
Would someone tell me why this does not work.
I have buttons for inputs on pins 4,5,6,and,7.
My LEDs are on pins:17,18,19, and 20.
I did a spin program, and it worked.

pub main
cognew(@IOtest,0)

dat
               org 0
 IOtest      mov dira, pin        
 loop        mov outa,ina
             jmp #loop
 pin   long  %00000000000011110000000000000000

I read Mr Potatohead's article " Assembly Language Primer".
Would someone suggest other readings covering assembly language?

kuroneko · 2010-09-30 06:38

In SPIN you probably did something like outa[17..20] := ina[4..7]. You don't do this in PASM. Try this:

pub main
cognew(@IOtest,0)

dat
               org 0
 IOtest      mov dira, pin        
 loop        mov outa,ina
             shl outa,#20-7
             jmp #loop
 pin   long  %00000000_000[COLOR="Red"]1[/COLOR]111[COLOR="Red"]0[/COLOR]_00000000_00000000

Do you really mean 17..20? If so your pin mask is off by 1.

Pliers · 2010-09-30 06:48

Thanks for the quick reply.
I just barley understand why I need the shift left.
I'll give it a good study.
Thanks again.

kuroneko · 2010-09-30 06:52

Pliers wrote: »

I just barley understand why I need the shift left.

In PASM you read all 32bit of ina. Which means that the bits you're interested in are down here %00000000_00000000_00000000_????0000. Somehow you have to get them up to here %00000000_000xxxx0_00000000_00000000, so you have to shift them left a bit.

LukeH · 2010-09-30 07:01

Likewise, in asm, when you MOV something to OUTA, you write all 32 bits of the register (for the cog you're in). Thus if you want to control only one of several leds controlled by the same cog, you would need a different instruction. OR and MUXZ come to mind. Neither of them are needed for what you're immediately trying to do right now, but you will need those instructions soon for more advanced programming.

Practice! ASM is hard to wrap your brain around at first, but once it "clicks," it's easy and fun. Check out the "Getting Started and Key Thread Index" thread near the top of this forum for links to some good ASM academics and examples.

Simple Assembly

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