From: William Levak (wlevak_at_cyberspace.org)
Date: 2004-04-13 06:32:44
On Mon, 12 Apr 2004, Larry Mollica wrote:
> Hi all. I'm wondering if anyone has experience with, or knows of a source of
> information regarding using the PET to control Hewlett Packard test equipment.
>
> I need a way to send specific "bus commands" to the HP gear.
> >From what I gather, bus commands are essentially like sending regular data
> except that the ATN line is held low. If there's a way to do this within PET
> basic, it has escaped me.
>
> I'm thinking that it should be possible to brute-force bus commands by POKEingto
> the PIA such that it simulates sending data with ATN low. It could probably
> cheat some steps too, like using a timing loop rather than looking for proper
> bus hand shakes, etc. There are only a few bus commands I need to send, mostly
> to release control of the instrument front panel.
>
> I'm hoping someone has already figured this out and knows how to do it...
ATN out is bit 2 at 59456 (6522 interface). The direction register for
this port is at 59458.
You may be able to change a few control lines, but to really use the
interface, you need to use the machine language routines in the ROM's.
BASIC is just too slow.
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