Recreating a HP-25

[PANAMATIK]

(10-26-2016 07:21 PM)Alejandro Paz(Germany) Wrote:  These last days I was able to get to work again on the core, and to iron out those bugs that prevented STO/RCL and the block-memory based register file to work. I ended, as I suspected, having to add a couple extra cycles to account for the block ram latency. Now, it works as a real 25 would do but much faster. Sadly a bit late for the meeting .

Now I have a question, is the firmware of the 25C different from the regular non-C model ?

Congratulations for having the STO RCL issue fixed!

Your prototype didn't seem to have a PRGM/RUN switch. I couldn't enter program steps. Pressing SST or R/S button didn't show the next program step when hold down. Did you fix that too? You just have to set status bit s 15 every instruction as long as any key is hold down.

HP-25 and HP-25C have the same firmware, the only difference in behaviour occurs as the RAMs of the C model doesn't clear its contents when "clear data regs" is executed.

Bernhard