At 05:14 PM 8/18/99 +0200, you wrote:
>Hoi Sean,
Sean's address is not "[EMAIL PROTECTED]", probably an error in your address book.
But the questions are interesting, so I'll answer as much of them as I can.
>Dit FH bit hangt ook samen met register#19 (interrupt line register). Ook
>de volgende hebben hier iets mee te doen:
>
>reg#0, bit 5, Interrupt Enable 2 (ook voor lichtpen)
>reg#0, bit 4, Horizontal scanning line, Interrupt Enable 1
>reg#1, bit 5, Horizontal scanning line, Interrupt Enable 0
The V9938 contains an error there: reg#1, bit 5 is for the vertical retrace
interrupt (50/60Hz).
About FH (status reg 1, bit 0):
If the VDP scanning reaches the line specified in reg#19, the FH bit set.
If the IE1 (reg#0, bit4) is enabled, an interrupt is generated. So the
setting of FH does not require the line interrupt to be enabled.
>Is interrupt aanvraag die is opgewekt d.m.v. het gebruik van register#19 ook
>op deze manier te cancellen door simpel weg status#1 te lezen, welke volgens
>de documentatie een reset veroorzaakt van het FH bit.
>
>Sommige demos lezen dit FH bit maar zonder gebruik te maken van de eigenlijk
>bijbehorende interrupt.
I think most code that reads FH but doesn't use the interrupt, doesn't
enable the interrupt either.
To find out if an interrupt can be cancelled, the best way is to write a
test program.
Bye,
Maarten
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