At 10:13 PM 2/22/99 +0100, you wrote:
[about using IM2]
>You should set your
>interruptpointer at address #C0FF instead. As some of you might know, the
>databus in the MSX is connected to VCC with pull-up resistors. As a
>consequence the Z80 will always fetch the value 0xFF when reading from the
>databus at a moment that no device is writing to the databus. For example,
>when the Z80 reads the databus in IM2 after having received an interrupt
>request.
Years ago, one of the NOP programmers told me that some devices do write a
value to the databus during an interrupt. To make sure your program will
work in any configuration, you need to fill 257 bytes with the same value.
For example #81 for a routine at #8181.
Bye,
Maarten
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