#: 8387 S12/OS9/68000 (OSK)
    23-Nov-90  21:05:00
Sb: #8347-#Atari-ST file transfer
Fm: BILL HEALTON 73367,357
To: David Betz 76704,47 (X)

David, OS9 Insights is a must with some  docs for the 68901. Also
the Abaqus book on Atari ST internals is very useful. Uniquenesses of the ST
/OSK include the location and activation of exceptions. OSK sets up its own
exception vector table. It has the entry form of:
                   PEA  #Exception Address  (Exception Number * 4)
                   JMP  Longword Vector Address Each entry is (10) ten bytes
long. The table starts with vector #2 Addr=$0008 The table is located starting
@ -$1000(A6) (A6 is Global set by OSK). In order for OSK to handle the
exception, th driver must calculate the entry address for the exception
(#-2)*10+(-$1000(A6)) and place it at the vector address in low RAM (#*4). The
"OS9 F$IRQ" call (doc'd in Tech manual) will set the Longword Vector Address.
Another useful Manual would be the new OSK Technial I/O Manual.

Particulars of the 68901 are included in the ST internals book or motorola
doc's. Timer D is used to set the Baud Rate(no Timer D IRQ). Otherwise the
RS232 portion should be the only portion touched (by anding and or-ing where
necessary). Good luck and let me know if you decide to try it and need more
info.

Bill Healton 73367,357

There is 1 Reply.