27 Mar
2008
27 Mar
'08
9:03 a.m.
Rod Smallwood wrote:
Hello All
As I said before my PDP-8/e partly failed insofar as it would
not load data into memory.
I rewound my personal memory back thirty plus years and did a lot of
relearning about how pre microprocessor systems worked.
Toggling the Add Load switch puts the address on the bus and triggers
the time state generator to cycle.
In the correct time slot the address is set in the memory ready for the
data.
Setting the Switch Register with the data and toggling the DEP key
should write data from the SR to the pre set memory location via the bus
in another time slot.
The time states are generated by a string of SN74194 shift registers and
the slot for the data is not being decoded. It looks like the '194 is at
fault.
Now I need either a couple of 74194's or an M8330 board.
TTL can be found here:
http://www.unicornelectronics.com/prod.htm
Rod Smallwood
TheDECcollector