9960 Extender questions

[Haggis]

Hi, I was wondering if anybody could answer the following questions:
1) If I use a register PUSH and a POP the extender becomes unstable when executing the protocol which contain those instructions. I wouldn't have thought that the stack was so sensitive.
2) What, if anything, is R74 used for? If it is being used, are there any free registers for me to use?

Thanks

[johnsfine]

1) If I use a register PUSH and a POP the extender becomes unstable when executing the protocol which contain those instructions. I wouldn't have thought that the stack was so sensitive.

The stack isn't that sensitive. You must have misused the PUSH/POP in some way. If you post the protocol that caused the problem, we can probably spot the error.

2) What, if anything, is R74 used for? If it is being used, are there any free registers for me to use?

That takes a little more research than I have time for right now. Hopefully someone who knows will answer.

Without the extender, I think R74 is used as part of the timer for advancing to the next channel while the Fav operation is in progress. I assume the extender eliminates the ability to activate that form of Fav. But I don't know whether that change makes R74 safe for other uses. Leaving a nonzero value in R74 might make the remote think it's in the middle of doing a Fav operation.

[Nils_Ekberg]

Using PUSH and POP in a protocol should have no impact on the extender. John is probably right (usually is) so if you post the source we can get a look at it.

I remember that in the 9960 R74 is used as an alternate status register for a variety of routines within the remote. It is not safe to use it for anything.

[Haggis]

Thank Nils, John. I had a bit of a branching problem that caused a non matching of pushing & popping. This means that a temp register is no longer required.