[Simh] Error in DMC11/DMR11 Emulation in RSTS/E 10.1

[Paul Koning]

> On Jan 3, 2016, at 6:42 PM, Christian Gauger-Cosgrove <captainkirk359 at gmail.com> wrote:
> 
> On 3 January 2016 at 16:42, Paul Koning <paulkoning at comcast.net> wrote:
>> No, that's not what that means.
>> 
>> It does say that micro diagnostics are required; when those are disabled, the device is rejected because of that failure.
>> 
> Note that XM0 and XM1 provide the same "XMn: is missing ECO's, but
> will still function" as XM4; and XM4 has the micro-diagnostics
> DISABLED all three of those devices are TYPE=DMC and INIT accepted all
> three. The rejected devices are XM2 and XM3 which were defined as
> TYPE=DMR (one with and one without micro-diagnostics).

I found why.  In pdp11_dmc.c, if a master clear is done on a DMR that is not currently attached, a micro-diagnostic failure status is posted.  

I'm not sure if that's a good idea.  In RSTS, this test happens at boot, and if at that time you're not attached, the device will be disabled because of that failure status.  Attaching later on then won't help.  It may be better for unattached to produce some more benign status (or, perhaps, simply to result in no communication so DDCMP startup will time out in the same way it would if the remote system were down).

So attach the device in SIMH before boot, and things will work.

Note that micro-diagnostics must be ENABLED for RSTS to work.  If it sees them disabled, it tries again; if they are still disabled (which of course they will be) that is treated as a failure and the DMR will be disabled.

	paul