__PARAMCNT during interrupt; use of __INTPARAMFSR
Zoot
Posts: 2,227
On my ISR-based SX projects, I generally use a NOPRESERVE for the ISR and assembly code for most of the ISR itself.
However, I have one project where I want to use the param registers in both the ISR and the mainline program.
In looking over the source code generated by SX/B, I noticed a few things that I need clarification on:
1. it appears that only PARAM1 - PARAM4 are preserved in the INTPARAMFSR registers; PARAM5 (aka __PARAMCNT) does NOT appear to be preserved. Since it seems to be common practice in SX/B to use __PARAMCNT, it would seem that if an interrupt occurs during the first few lines of something like the following, then you could be trouble. Or am I missing something? I generally use ASM and do not use the param registers in my ISRs, but still...
2. since PARAMS are "preserved" in the __INTPARAMFSR registers during an interrupt, IF I AM DECLARING NOPRESERVE, it looks like I could claim back these registers for my own purposes? It appears (in my generated .src output anyway) that __INTPARAMFSR is declared and the var space is assigned whether or not is used?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
When the going gets weird, the weird turn pro. -- HST
1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php
However, I have one project where I want to use the param registers in both the ISR and the mainline program.
In looking over the source code generated by SX/B, I noticed a few things that I need clarification on:
1. it appears that only PARAM1 - PARAM4 are preserved in the INTPARAMFSR registers; PARAM5 (aka __PARAMCNT) does NOT appear to be preserved. Since it seems to be common practice in SX/B to use __PARAMCNT, it would seem that if an interrupt occurs during the first few lines of something like the following, then you could be trouble. Or am I missing something? I generally use ASM and do not use the param registers in my ISRs, but still...
SomeSub:
IF __PARAMCNT = 1 THEN
tmpW1 = __PARAM1 ' if interrupt occurs here, and paramcnt is used by SX/B operations in the ISR, then it could get mucked up ????
ELSEIF __PARAMCNT = 2 THEN
tmpW1 = __PARAMW12
ENDIF
2. since PARAMS are "preserved" in the __INTPARAMFSR registers during an interrupt, IF I AM DECLARING NOPRESERVE, it looks like I could claim back these registers for my own purposes? It appears (in my generated .src output anyway) that __INTPARAMFSR is declared and the var space is assigned whether or not is used?
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
When the going gets weird, the weird turn pro. -- HST
1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php
Comments
1) I think you are correct. __PARAM5 should be preserved as well. I'll look at the current beta to see if it is.
2) If you are using NOPRESERVE then you could use the locations at __INTPARAMFSR for you own use.
Bean.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Did you know that 111,111,111 multiplied by 111,111,111 equals 12345678987654321 ?
www.iElectronicDesigns.com
·