Keyboard int (PORTS)

[Asman]

I saw few times following situation in PORTS int ($68 + vbr).
1. read keycode from $bfec01
2. clear or set $ff to $bfec01
Mean

intPORTS:
        moveq #0,d0
        move.b $bfec01,d0
        clr.b $bfec01  ; move.b #$ff,$bfec01

        ....
        rte

I've no idea why somebody clear or set $ff to $bfec01. Is there any explanation of it ?. Is it ok do this ?

[Exodous]

After reading the value, one of the bits needs setting to acknowledge they key has been read. See this thread http://eab.abime.net/showthread.php?t=102943 for more details.

[ross]

Hi Asman,
you can overwrite keycode in $bfec01 (CIA registers are r/w).
So if an external code (out of IRQ) get it, a $00 or $ff is read.

[Toni Wilen]

Looks like too simple key read code. If new code is zero or ff = no new key, skip. Checking CIA interrupt bits is too difficult

[ross]

Originally Posted by Toni Wilen

Looks like too simple key read code. If new code is zero or ff = no new key, skip. Checking CIA interrupt bits is too difficult

it is normally used this way.
Lazy coders

[roondar]

All coders are a bit lazy, right?
Otherwise why spend all that effort to get the computer to do stuff for us instead of doing it ourself?

[ross]

Originally Posted by roondar

All coders are a bit lazy, right?
Otherwise why spend all that effort to get the computer to do stuff for us instead of doing it ourself?

And as the AtariST coders always say, the Amiga ones are especially so