Paul James E. wrote:
>  A question about the 10 bit AD on an F877.  Referring to the code
>  snippet below, looking at the line indicated ( by **--->), can anyone
>  explain why when this reads 'bsf   STATUS,RP0', the program hangs
>  apparently at that line.   If we change it to read 'bcf   STATUS,RP0',
>  the program don't hang,

I'm not going to check whether you are manually trying to set the right
banks.  This sort of thing should be left to the assembler.  It knows the
exact address of each SFR and can therefore emit the appropriate code to
switch to the right bank.

At the very least use BANKSEL so that people trying to help you don't get
distracted by bank setting issues.  A better answer is the DBANKIF and
related macros in STD.INS.ASPIC at http://www.embedinc.com/pic.

> RdVrp   ; read ASIC pos ref voltage
>         errorlevel      -302
>         bcf     STATUS, RP0                   ;bank 0
>         bcf STATUS, RP1

Should be BANSEL ADCON0, or DBANKIF ADCON0, at least when you're asking
others to look at your code (see above).  Again, I'm not going to verify
that you really want bank 0 here, although this is where the bug is more
times than not.

>         movlw   B'01001001'                   ;Fosc/8, A/D chan 1, A/D
>         movwf   ADCON0
>         bsf     ADCON0, GO

You didn't leave anywhere near enough acquisition time here.

>         movlw   D'1'
>         call Wait

Does WAIT effect the bank setting?  In general you should invalidate your
bank assumptions after a call.

> VrpWait
>         btfsc   ADCON0, GO

You are assuming a specific bank here, but it's not obvious the bank
settings aren't completely trashed at this point.

>         goto    VrpWait
>
>         bcf     STATUS, RP0

And RP1?

>         movf    ADRESH, W
>         movwf   AccaH

And the bank of ACCAH

>  **---> bsf     STATUS,RP0                      ; goto page 1

I seriously doubt this instruction is hanging the machine.  How did you
reach that conclusion?

> Does anyone have any ideas to try that I haven't mentioned?

You need to clean up your banking act.  Other issues are a waste of time
until that is done.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads