28 Nov
2007
28 Nov
'07
4:24 p.m.
[Tandy CoCo]
Hmm, interesting. Is that the one that was the same as
the Dragon 32 in the UK
(i.e. built from the 6809 app note)?
Similar, but not the same. Yes, they are both based on the same
application note for the 6883, but there are differences. The main one is
that the Dragon has a Centornics port, the CoCo has a serial port. Both
make use of the 3 otherwise unused PIA lines. On the CoCo, they're used
for the bit-banged RS232 port, on the Dargon, they're the Stb/, Busy and
Ack/ lines o fhte Sentornics port, the data for which comes from the
keyboard scan output port. Since the keyboard input is ignored during
printing, and the printer only looks at data if STB/ is asserted, this
causes no problems.
The other differnce is that he BASIC ROM is different. In particular the
tokens are in a different order (so a binary program CSAVEd on one
machine will not CLOAD into the thother). Some plug0-in ROMs, including,
I usepct, the disk contorller, don't work in both machines. Don't expect
your Dragon disk interface to work in a CoCo.
-tony