I now have successfully dumped all 8 2708 EPROMs of my FESTO programming device.
Interpreting that firmware is another thing. I haven’t found any text although the device is able to disassemble and put out the mnemonics.
I’ve checked ASCII, EBCDIC and early IBM encodings (6/8-bit BCD etc) like in Rob Storey’s/Paul Pierce’s FILEUTIL/ FILEBROWS. I think, I’ll make a detailed thread about that later, I also have to recheck the manual and convert to octal words or to 12/14 bits. I found some firmware analyzing tools like BINWALK, but haven’t tested them, yet. Maybe it needs to be converted to Intel Hex or similar or it’s encrypted. I found a converter for BIN files on sourceforge for Siemens Step 5 (but probably not compatibel).
There’s another, single 4K EPROM from Intersil on the lower PCB (left on my photo). IM6654A (CMOS 512x8).
I have the Arduino programmer which can only read (and write) 2708 and MCM68764 as described by Matt Millman.
Programming the Intersil is definitely not possible (Vpp -40 V). But maybe reading?
I’ve read the EPROM datasheets and I think it’s not possible, maybe someone can confirm it. Intersil chips were (also) made by Harris.
The 2708 specs has at Vss -5V and VDD +12 V, so I think that’ll not work.
The MCM68766 has VCC 4.5-5.5 V (AC or DC?). There’s a different PIN assignment but that is changed via a switch as well.
The Intersil EPROM needs 10V as it’s IM6654A (IM6654 needs 5 V).
The DC characteristics: VCC=VDD=4.5-10.5 V
The AC characteristics: 10 V ±5%
I know it’s alternating/direct current, but what is used here when reading? I would say direct.
I haven’t checked the timing. But the main question next to the voltage is the PIN assignment what is almost like the 2708. It’s also a different size.
If possible, I want to use the same programmer and not alter it, in case I want to read or write 2708 again.
Due to the location of the EPROM in the FESTO device, I assume i/o functions (memory cartridge/teletype/tape), so not that important.