newbie, trouble with RTI

[Dietrich]

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Date: Mon Mar 7, 2005 7:56pm

Subject: newbie, trouble with RTI

    using mc9312c32 on techarts 12max nanocore board. compiling in
codewarrion, writing to chip with ubug12 serial comm. I am trying to
use a real time interrupt to sample 256 data points for fft. The
relevent code follows - i have omitted most of my program as it is
getting quite lengthy.

GETDATA:
movb #$00, DPOINT
ldx #DATA
movb #%01110000, ATDCTL
movb #%00110000, RTICTL
bset CRGFLG, #%10000000

DLOOP:
ldaa DPOINT
cmpa #$FF
beq FFT
bra DLOOP

RTI_SUB:
ldaa ATDDR1H
staa 1,x+
inc DPOINT
bclr CRGFLG, #%10000000
rti

; Interrupt Vectors
Org Vreset
fdb ResetFunc
ORG Vrti
fdb RTI_SUB

rest of program runs fine - as soon as i enter 'GETDATA:' controller
seems to lock up - any thoughts?
 

Date: Mon Mar 7, 2005 9:46pm 
 
    In your GETDATA: label you incorrectly attempt to start the RTI by
setting bit 7 of CRGFLG hi. It believe you actually need to set bit
7 of CRGINT hi to kick start the RTI.

At the end of your RTI interrupt you need to write 128 to CRGFLG to
reset the interrupt flag. You are now clearing that bit.

Date: Mon Mar 7, 2005 10:11pm 
 
    I appreciate your review - i have corrected these mistakes - however,
my code still seems to get stuck in the DLOOP: without any interrupts
occuring, any ideas?

Date: Mon Mar 7, 2005 10:33pm
 
    Sorry, was just looking a RTI issues before.

In your RTI interrupt it looks like x is free in increment far
outside your intended data structure, mowing down everything in its
path. Remember that the RTI never stops, even though other parts of
your software stop gathering data. DLOOP stays inside the 256
element range because it's a byte and rolls around inside your data
structure, but x is 16 bits. You need to rethink the relationship
between the RTI and your "foreground" routines.

Date: Tue Mar 8, 2005 10:31am
 
    this makes sense - that's why my first instruction upon leaving DLOOP
(which i hadn't shown previously) is to disable RTI.
thanks everyone for the help - i'll see if i can get this going
today....

Date: Wed Mar 9, 2005 9:57pm

    Real time interrupts are working great now- thanks to all for the
suggestions and the help!

Date: Mon Mar 7, 2005 11:30pm

    >> > movb #%00110000, RTICTL

You didn't enable RTI. Bits 6:4 and 3:0 of RTICTL should be non zero