Xerox 820 system disks in Teledisk format?
ard at p850ug1.demon.co.uk
Fri May 8 12:59:02 CDT 2009
> > PS. I like the 6809 and OS/9...
Add me as another OS-9 fan. I ran it first on a CoCo2 (64K) and found the
I/O system amde it very easy to write device drivers for custom hardware
(and guess what I kept on adding to my CoCo...)
> * Dragon 32's were to all intents and purposes the same as a Tandy CoCo I
There are some minor differnces, but both were based on the same Motorola
application note for the 6883 (SAM) and use essentially the same chips.
The main hardware differenve is the printer port. When the PIA lines
needed for the keyboard, cassette, video control, etc had been allocated,
there were 3 lines left. The CoCo uses them to make a bit-banged RS232
port (TxD, RxD, CD IIRC). The Dragon uses them to provide the Stb/, Busy
nad Ack/ lines for a Centronics port. The Centronics data comes from the
8 lines also used to scan the keyboard. Since the printer only looks at
those lines on the falling edge of a strobe (which doesn't happen while
the keuyboard is being scanned) and since the keyboard is not read when
the machine is sendinf data to the printer there's no problem.
One annoying difference is that the BASIC tokens are differnt. So while the
CoCO and Dragon can read eaxh other's tapes, and while you cna transfer BASIC
programs saved in ASCII with no problems, you can just load a tokenised
program saved on one machine into the other.
> believe. The D64 added a serial port and more memory (and in the case of OS/9,
> a cartridge-based FDC) over the D32.
IIRC the disk controller owrked with the Dragon 32 as well, but you
needed 64K to run OS-9
The Dragon 64 serial port was a real hardware one, based on a 6551 IRRC.
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