[Coco] Q: Field Sync Interrupt

[Robert Gault]

Torsten Dittel wrote:
> Hi,
> something on-topic ;-):
> 
> What happens exactly, if you write to Bit 7 of $FF02? I know this Bit is
> the Field Sync Interrupt Flag which (if interrupt enabled in the CC and
> in Bit 0 of $FF03) is set when an interrupt occurs each 16.67ms and has
> to be cleared by reading from address $FF02 within the Interrupt Service
> Routine to allow further IRQs.
> 
> Thanks and regards,
> Torsten
> 
>
First the Field Sync Interrupt Flag is bit 7 of $FF03 not $FF02 as you 
said. Did you mean "write to $FF03"?

If there is any effect by writing to bit 7 of $FF03, it would be 
transitory not lasting past whatever monitors the flag.

Writing to bit 7 of $FF02 is done during the keyboard strobe.