Hi everyone,

Im in a bit of a pickle!
Just about every register in the Z80 can be saved with the exception of the stack pointer, that is, it can only be written to :/

Does anyone know of a way to save the position that the stack pointer is currently pointing to? For example, a instruction that I would have loved in the Z80 would be LD HL, SP where HL gets loaded with the value of the SP register.

Many thanks guys,
Robin

 

Does anyone know of a way to save the position that the stack pointer is currently pointing to? For example, a instruction that I would have loved in the Z80 would be LD HL, SP where HL gets loaded with the value of the SP register.

How about:

	LD	(SPBUFF),SP
	LD	HL,(SPBUFF)

Where SPBUFF is the address of a 2 byte RAM location?

 

That'll do it.

 

Well, im really happy now

Thanks sooo much!

 

Well, im really happy now

Thanks sooo much!

You're welcome.

I had to dig up some code from 1980 (I was 13 at the time) to remember how to do that. I wrote a tape base "operating system" for the TRS-80, and it included a machine language monitor/debugger. I used that sequence of instructions to capture and display the stack pointer value after a break point.

 

Wow, I'm impressed that you still have code from 1980 all my Z80 stuff is long gone.

 

Wow, I'm impressed that you still have code from 1980 all my Z80 stuff is long gone.

I lost a lot of stuff, including my original customized TRS-80 Model I. Very depressing. I've got a lot of yellowed printouts, though.

 

I was pretty sure I had seen this in one of Jack Ganssle's books on an RTOS for the Z80. He definitely had separate stacks for each task.

http://www.amazon.com/exec/obidos/ASIN/0122748808/thegansslegroup

$7.78 + shipping is a bargain!!