9 Mar
2016
9 Mar
'16
9:45 p.m.
On 03/09/2016 08:43 PM, Chuck Guzis wrote:
On 03/09/2016 08:49 AM, Jon Elson wrote:
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
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.