From: "Andrew Lynch" <lynchaj at yahoo.com>
Sent: Sunday, November 15, 2009 10:40 PM
To: <cctalk at classiccmp.org>
Subject: Motorola EXORset
Hi! Does anyone have the schematics for the Motorola
EXORset? If so,
would
you please either make a scan or look something up for me?
I would like to know how the MC6840 PTM interfaces with the MC6809 CPU.
Thanks and have a nice day!
Andrew Lynch
It is fairly straight forward, as with all 68xx chips.
The databus goes to ... the databus.
The E clock input connects to the E (sometimes called phi2) of the 6809.
The RSx pins go to address lines, depending on your decoding scheme.
The normal method is RS0 to A0, RS1 to A1 and RS2 to A2.
R/W* goes directly to the R/W* pin of the CPU.
CS0* and CS1 go to address decode logic. The chip is selected when
CS0* = "0" and CS1 = "1".
If you want to use interrupts you must tie the IRQ output of the PTM to
the IRQ input of the CPU. As several peripheral devices can be connected
to the IRQ pin of the CPU, they are all open collector. So somewhere the
IRQ line must have a pull-up resistor.
- Henk.