On 03/09/2016 08:43 PM, Chuck Guzis wrote:
On 03/09/2016 08:49 AM, Jon Elson wrote:
The row of red LEDs at the bottom of the pic is the front
panel of
the 7300 CPU. They had an industrial control bus that
allowed you to
connect a wide variety of interface boards, like encoder
counters,
DACs, digital inputs and outputs, etc. It used
battery-backed DRAM,
and was made around 1978.
Much of the old Mitsubishi CNC gear uses battery-backed
RAM via a lead-acid storage battery "floated" on a
supply. A tape or diskette drive is used for loading it
with parameters and software. Once read, the floppy isn't
used for regular operation.
The A-B was loaded from paper tape. I didn't get the CNC
executive with it, just the CPU diagnostics.
I found a guy on the net who serviced these oldsters and
made a tape on one of his customer's machines.
I then had to write a disassembler and patch the code to
make it work on my specific setup. Mostly, I had to change
the encoder resolution. Lucky for me, it was only a 2:1
change. I quickly built a "BTR" (behind the reader)
interface to a laptop, and used it to download the executive
and then it drip-fed the CNC program a line at a time to the
A-B control.
When CPU power was off, the DRAM arrays were powered up 640
times a second and a complete refresh cycle was done, then
the DRAMS were powered off again. If you leaned close to
the memory power supply, you could hear the 640 Hz tone.
Jon
