asm and ram hub adress

henrib75

Hello everyone,
I'm just starting to do some interesting things with the Propeller, so I have a silly question… I'd like to have a compiled assembly program in the RAM hub (which doesn't run) after initialization, and then have a cog load this code snippet from its memory address and execute it. This is simple with another MCU, but I don't know how to do it with the Propeller. I want to emphasize that I need to be able to launch it from its address (not a DAT spin block whose location I don't actually know…). Perhaps it's simple?

Thanks

PS: This is an automatic translation

JonnyMac

Perhaps it's simple?

Yes. The @ symbol gives you the address of code in a DAT block (which lives in RAM and can be copied to one or more cogs).

For example, here's a simple 50% duty-cycle flasher for a pin.

dat 

                        org       0

flashpin                mov       t1, par                       ' point to parameters
                        rdlong    t2, t1                        ' read pin
                        mov       pinmask, #1                   ' convert to mask
                        shl       pinmask, t2
                        or        dira, pinmask                 ' set to output
                        add       t1, #4
                        rdlong    delayticks, t1                ' get 1/2 cycle ticks

                        mov       t1, cnt
                        add       t1, delayticks

loop                    or        outa, pinmask                 ' led pin high
                        waitcnt   t1, delayticks
                        andn      outa, pinmask                 ' led pin low
                        waitcnt   t1, delayticks
                        jmp       #loop
                                       ' 

' --------------------------------------------------------------------------------------------------

pinmask                 res       1
delayticks              res       1

t1                      res       1                             ' work vars
t2                      res       1
t3                      res       1

It needs two consecutive longs to provide the pin # and the half-cycle delay in ticks

var 

  long  flasher
  long  ticks 

Set the pin and delay and then start with cognew()

pub main

  flasher := 26
  ticks   := CLK_FREQ >> 1

  cognew(@entry, @flasher)

  repeat
    waitcnt(0)

This is in fact doing what you ask for:

• Code defined in RAM (DAT sections are pre-initialized RAM)
• @ provides the address of your code
• cognew runs that code it a separate cog

Just a note: If you want to know if your cog loaded and what cog it's in, this is the standard practice

  cog := cognew(@entry, @flasher) + 1

If cognew() works then cog will be > 0 (evaluates as true), otherwise cog will be 0 (false). If you want to shutdown that cog

  cogstop(cog-1)

You can use coginit() to load a specific cog.

henrib75

Thanks. Yes, I know how to do that, but I want to be able to assign an address as a hexadecimal number, like when you start a Cog program in assembly... but in Spin. And above all, how do I put compiled assembly code at a specific address in the RAM hub?

Rayman

Guess you could first copy the assembly to that fixed place and then load the cog from there? Maybe that would work?

That kind of goes against the grain for the Parallax Spin.

FlexProp's spin has an absolute address operator that might make things easier. I know if from P2, but think works with P1 too...

henrib75

Yes, I could copy to a specific location, but how? In Spin, I can't provide a hexadecimal address using Longmove? And how can I know the length of the compiled DAT file? And how can I avoid writing to the Spin code that's currently executing, since I don't know its address either?

Rayman

If you are using the Prop Tool, you can do info and see the memory map. Just stay a bit away from the very end because Spin uses that for stack space.

I'd just copy 512 longs, that way can make sure it's all there...

Longmove should work?