On 2013-06-02 20:01, Tony Duell wrote:
The inter-processor link in the HX20 itslef is
somewhat similar. There's
a serial port o nthe main CPU that can be switched either to the slave
CPU or to the serial socket for the disk drive, etc.
channel B is not used. So connecting my
TTL-to-USB to the TXDB and RXDB
and boot the TF-20: alas no output or any reaction to Enter, Esc or Ctrl-C.
By now I know the boot ROM does initialize channel B, but does not write
to it. Apparantly TFDos doesn't either.
Pity :-(
Hopefully tomorrow I have time to connect a PX-8 or HX-20 to it, maybe
that triggers a response.
I don't know if there's any Digital Research code in the TF20 OS, but it
wouldn't suprise me, BTW. It seems to be very similar to CP/M.
Here is track 0 from the disk image:
http://fjkraan.home.xs4all.nl/comp/tf20/tfdos_trk01.bin. It does contain
some BDOS like text: "Bdos Err On : $Bad Sector$Select$File R/O$"
-tony
Fred Jan