> "When my program blows up randomly, the first thing I look for is..."
>=20

An emulator with TRACE possibilities :-)

Stack overflow.

Bank and page switching.

Interrupt routine messing with noninterrupt variables or=20
routines.

One thing that has bitten me a couple of times: Interrupt=20
routine that directly sets an IO pin of a port that is also=20
managed by the main program while it is temporarily holding the=20
port value in a register.=20

Code for main program:

1:      mov             w,#BITMASK
2:      and             w,PORT
3:      do something to the port value here
4:      mov             PORT,w

If you get an interrupt that also sets an output in this port=20
register at step 3, it is lost as soon as the interrupt is=20
returning and step 4 is executed.

Ruben=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D
Ruben J=F6nsson
AB Liros Electronic
Box 9124, 200 39 Malm=F6, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
ruben@pp.sbbs.se
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D

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