7 Aug
2011
7 Aug
'11
1:06 p.m.
To test the tape drive, I used the programmer's
console on my PDP-11/05 to
issue a read command to a mounted tape. When I issued a read command by
depositing a command into the TMA-11 command register, the tape advanced
slightly and then stopped. The 'Bus Grant Late' error was set in the TMA-11
status register. The status register did indicate the controller and tape drive
were both ready. No data was read in.
Were you toggling in commands on the front panel with the CPU halted? I
seem to remmber that some PDP11s will not handle bus requrests / NPRs if
the processor isn't running, and thus if you try to operate such a
peripheral in this wa, you will get a 'late grant' problem. It's better
to enter a short program from the panel and run that. All the program
needs to do is deposit the correct device command word in the right I/O
location (you can set up all the other values -- the address, word count,
etc -- from the panel) and loop either until the device indicates the
command has completed, or just loop forever, and you can halt the program
after a suitable time and examine device registers, memory ,etc.
The read command was issued while the processor is halted.
This particular system did not originally have any external devices hooked up
to it.
Beginning at the processor, the system has the following components installed:
KD11-B PDP-11/05
LS11 line printer card (connects to a Centronics 101A printer)
MM11-U 16K x 16 core memory
MM11-U 16K x 16 core memory
RK11-D RK05 disk controller
(See http://www.iamvirtual.ca/collection/systems/minis/PDP11-10/Boards.html
for details)
The BC11 cable leading to the TMA-11 controller is put on the Unibus
out connection
at the last slot of the RK11-D controller.
Based on previous posts from others, I suspect I don't have the processor grant
set up correctly.
My first question is 'Does the RK05 work correctly?'. The RK11-D is an
NPR device too, so if its's working, grants must be getting as far as
that. If the're then not getting to the tape controller, there must be a
fault either in the cable between those devices, or a fault in the RK11-D
itself (I have had a device that failed to pass on a grant, I think one
of the bus driver ICs had fialed. It was an easy fix, anyway...)
-tony