9 Jan
2009
9 Jan
'09
12:32 p.m.
Apologies for replying to my own post, but...
Commodore drives do some strange things with GPIB
addressing. Bit 7
isn't supposed to be used, but I think Commodore use it to add a flag to
the primary address when opening files. ISTR they may even use bit 6
this way, thus preventing you from having a device at (disk drive)+16.
If I had engaged brain before opening text editor, I would have realised
that this is bit 4 that is being misused. Bits 5 and 6 are correctly
used to say what sort of address it is - talk, listen, secondary.
Philip.