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'[SX]:How is this possible???'
2002\04\08@064811 by ISO-8859-1?Q?Ruben_J=F6nsson?=


Env: SXKey Rev E, SXKey52 V1.20, SX Chip SX52BD/PQ AB0022AT, 10 MHz crystal oscillator.

I have a problem which is about to drive me crazy.

I set a breakpoint at address 0x8b5 in the following piece of code:

8B0- 01D                bank            EECTRL
8B1- 076                clr             EECTRL
8B2- 02D                mov             TMP3,w
8B3- 20B 03A            mov             EESXADR,TMP1
8B5- 20C                mov             w,TMP2          ;TMP2 is at location $0c
8B6- 03B                mov             EEBYTECOUNT,w
8B7- 20D                mov             w,TMP3
8B8- 70A                sb              f_EE_READ_BLOCK_0
8B9- A55                jmp             eeprom_write
8BA- A76                jmp             eeprom_read

Sometimes when the program stops at this breakpoint (when instruction mov w,TMP2 has been
executed) W is loaded with a different value from what is at location TMP2 (as indicated by the
SX key)! Since TMP2 is at location $0c the bank selection bits are ignored for this load and can't
be the source of my problem.

When W is loaded with the wrong value RTCC indicates that the ISR has just been executed.
The only source of interrupt is the RTCC rollover interrupt. The ISR is exited with mov w,#-130,
retiw so this should not be the source if my problem either.

I have tried to set the breakpoint at the instruction at 0x8b3 and stepped through the ISR when
the rollover interrupt has occurred right after this instruction but have found no problem.

What could cause this behavior?

Ruben Jönsson
AB Liros Electronic
Box 9124, 200 39 Malmö, Sweden
TEL INT +46 40142078
FAX INT +46 40947388

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