> From: Megan
> Subject: Re: PDP11/0x in my apartment?
> Date: Thu, 4 Mar 2004 03:06:41 +0000 (UTC)
> X-MailScanner: PASSED (v1.2.8 80084 i24MxJu9001399 mailbox7.ucsd.edu)
> Carl Lowenstein writes:
> >Not to discourage you from wanting a PDP11 in your apartment, but
> >the 11/05 and 11/10 don't really have blinkenlights. They have
> >lights that display static information when the CPU is stopped.
> >I don't even think you can have the lights show the contents of
> >R0 during a RESET instruction, the way 11/20s do. For more blink,
> >you really want an 11/20 or 11/45.

> The 11/05,10 does indeed display the contents of R0 on a RESET
> instruction. I have heard a rumor (which I will have to test
> on my 11/05 when it comes out of mothballs in a few months) that
> the contents of R0 are displayed also for a WAIT. If someone
> knows for sure, I'm ready to be corrected...

I hope you're right. My experience with 11/05's was limited to
a few minutes poking at them at DECUS shows. When I got an
11/05/10/35/40 handbook off the shelf a couple of days ago to
check on this, I looked at

Table 8-1 Information Displayed in ADDRESS/DATA Lights (for 11/05)
and found the following information relevant to displaying data:

Condition Display
--------- -------
EXAM switch depressed Address of location to be examined
EXAM switch released Contents of selected address

DEP switch raised Address of location to be loaded
DEP switch released Contents of Switch Register
(which is the data deposited)

RUN Light on Undefined

HALT switch set Address of instruction to be executed
when CONT switch is activated.
HALT instruction executed (same as above)

That's about half of the table. Unlike the more classic 11/20,
no mention of display of R0 during RESET, WAIT, or HALT.
Specific mention of display of something not R0 during HALT.

Just looked at the 11/20 manual to refresh my memory. The DATA lights
show the contents of R0 during RESET and HALT, show nothing during WAIT.

Of course, maybe it's in the microcode and not in the manual.


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