[Simh] Configuring DMC11 Devices

[Paul Koning]

> On Jan 4, 2016, at 2:53 PM, Mark Pizzolato <Mark at infocomm.com> wrote:
> 
>> ...
> 
> I vaguely remember that something else depends on how it is currently implemented.  The wait delay was added to accommodate the fact that something didn't expect immediate response.  A delay of 1 is essentially the same as no delay.
> 
> It is hard to imagine that the OS driver would expect that the device would complete some operation in one instruction time.  This would tend to fail as newer models of CPU were implemented which used the same peripheral hardware, no?

All I can say is that it does work on real hardware.

The manual says that the bit is "self-clearing".  That isn't the same words as the more common "write only" but it implies roughly the same thing.  The driver definitely does not expect the whole master clear process to complete in a few instruction times; it patiently waits for RUN to become set.  But it DOES expect that MCLR does not read back as set, not even very quickly after it was set by the driver.

So maybe the thing to do is have the process master clear action be started at the CSR write rather than delayed (while other CSR operations can remain delayed) so that at least the clear_master_clear part is done right away.

>> By the way, if I connect a DMC to a DMR, it doesn't come up.  Is that
>> expected?  I thought DMC and DMR were sufficiently compatible that it
>> would work...
> 
> They absolutely should work as long as the both get turned on by software.  The wire protocol is the same.  The wire protocol is also compatible to host based DDCMP protocol implementations on the PDP10 and RSX since it can reliably talk to KMC/DUP configurations.

Ok, that's what I figured.  The wire protocols in the real hardware are actually not identical (DDCMP 3.1 vs. DDCMP 4.0, and in the case of the "high speed" DMC-11, 3.1 with some bugs that I might still have documented somewhere).  But yes, they are supposed to be interoperable.

Will investigate what's going wrong.

	paul