31 May
2001
31 May
'01
5:15 a.m.
John Foust wrote:
At 11:03 PM 5/29/01 -0400, Bob Shannon wrote:
The first implementation uses a small Z-8 based controller board wired to a
bank
of 74LS169 counters. These counters address several EPROMs that hold binary
images of the original paper tapes. A single EPROM is selected by a tape
selection
switch.
The Z8 also talks to some handshaking signals from an original HP Microcircuit
interface board jumpered to act exactly like the HP high-speed photo tape
reader
interface (but at TTL levels).
On request (control set) from the HP mini, the Z8 (programmed in tiny-basic)
handshakes
with the micro circuit I/F board to transfer the data from the EPROMs, and
increments the
74LS169 counters.
The Z8 had been 'hacked' to have non volitle RAM memory, but this has stopped
working
and the tiny-basic source (about 10 lines) needs to be reloaded each time the
power
is removed from the Z8.
I'm soon to replace the Z8 with a PIC16F877 that will also replace the TTL
address counters.
This enhanced version may also support reading physical paper tapes into flash
ROM, so I can make ROM images from original media using a generic parallel
interface tape reader I have laying around. The tape images I have now were
produced by connecting the Z8 to the reader, and sending the data to a PC
where it was burnt into EPROM.
For some reason, the image of BASIC I have does not load correctly, but I do
have good
images of OCTAPUS-C for the HP211x machines. Somehwhere I had the source code
for OCTAPUS, but I'm unable to locate it.
Lastly I have a collection of old software for
some of the machines (HP's
mainly). I have also
designed a photo-tape reader emulator that loads paper tape binary images
from ROM, so the old machines can be seen in action.
I'd like to hear more about that...
- John