On 2014-02-02 15:42, Robert Jarratt wrote:
As you may be aware I am trying to build an emulator
for MFM disks (mainly
DEC RD5x disks) using an FPGA. Things have been going moderately well in
that I have managed to get the MicroVAX 2000 formatter (TEST 70) to
recognise the appropriate RD5x disk by counting cylinders.
However, now I am at the stage when I want the controller in the 2000 to
write something. I am trying to use the formatter to write data to the disk.
However, the WRITE GATE signal never gets asserted.
I cannot see what is stopping the 2000 from asserting WRITE GATE. I have
implemented the Index signal which looks right on the oscilloscope, and of
course all the signals for track selection. I am sending dummy data on READ
DATA (all logical 0s as far as I can be sure). I am as sure as I can be that
I have the right pin on the connector (32 according to the 2000's tech
manual).
Just the obvious, but:
seek_complete is low?
ready is low?
track 0 is low?
index you said is OK,
write_fault is low?