Quote Originally Posted by kur4o View Post
I think that STY clear memory from 1400-15ff. It looks like it copies the value from 1400 and stores it[ $100 cycles word ] from 1400-15ff. 1400 looks like one of the injectors bpw so at reset should be cleared.

I think 16f0 needs more examination to figure what is going on at the hardware level. I am sure that 0003 sets some pin high or low on the ram chip, and some switching happens there. We have the microcode but no clue of the op codes it uses. Cracking the instruction set will open the door. Did you managed to define the memory range accessible to eside. I think that writing to the shared memory is a function of internal switching in the RAM chip. That extended ram chip might do more than we thought.
I posted yesterday but somehow it got lost. It's OK though because part of what I wrote was because of a programming error. I will try to re-write it but corrected.

The STY instruction stores content of IY register at the address IY points to. You would expect:

$1400 14 00 14 02 14 04 14 06
$1408 ....
.
.
.
$15F8 15 F8 15 FA 15 FC 15 FE

My thinking is that the upper byte is discarded and the lower byte used as a portion of the internal microstore address.

I have been working on the $16F0 register. I have been able to change it, change it back and have the part work. I tried writing to the microstore, but see no change in operation. This tells me that something (another register) is involved. I plan to work through that this morning.

-Tom