On 2013-06-01 21:31, Tony Duell wrote:
Yes. fasinating. I am trying to disassemble it, but started with the
boot ROM. The TFDOS as it is called, will be next.
I asusme you have a dump of the boot ROM? If not I think I can find it.
Yes, I have it:
http://fjkraan.home.xs4all.nl/comp/tf20/TFX.zip
It should eb fairly easy. There's absolutely nothign custum on there. All
standard chips, easy to get data sheets for them. A schematic exists, so
figurign ot uthe addresses of the I/O devices is not hard either.
I have never looked, there is that second serial port at TTL levels (th
TXDB and RSDB piads on the serial daughterboard). Does anything ever come
out of there in normal operation?
Only this evening I realized, based on your remark on the extra serial
port, that channel A is used for both host (HX-20) and 2nd TF-20 and
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.
-tony
Fred Jan
P.S. The boot ROM disassembly so far:
http://fjkraan.home.xs4all.nl/comp/tf20/TFX.asm
P.P.S.S. The movie I made of the SD-321 voice coil on the exerciser:
http://fjkraan.home.xs4all.nl/comp/tf20/sd-321_stepping.mpeg