one more question about pdp8/e console switches behaviour - test-drb@ccmp.vtda.org

10 Nov 2004

Thanks very much for the clear answer, Pete.
I have a webpage "in development", and hope to add a few pictures
representing the latest state of affairs. There is also a ZIP file
but it is an old version ... I will clean up the current source
(remove some debugging stuff) and make that available for download
as well. If you have a working Core Board *with* the extra 16k RAM
chip, you can run the pdp8/e simulation without the I/O Board by
just assembling the source with the "RealCons" conditional set to 0.
The wiring details (and more) are all in the source file.  The link
to the page is: www.pdp-11.nl  -- the click on [Homebrew 'PDP-11']
in the menu at the left, and on the page that opens click the link
[spin off] at the top right.

  enjoy (?),

- Henk, PA8PDP.

...
  -----Original Message-----
 From: cctalk-bounces(a)classiccmp.org
 [mailto:cctalk-bounces@classiccmp.org]On Behalf Of Pete Turnbull
 Sent: donderdag 11 november 2004 9:08
 To: General Discussion: On-Topic and Off-Topic Posts
 Subject: Re: one more question about pdp8/e console switches behaviour

 On Nov 11 2004,  8:32, Gooijen H wrote:
    Hello all,

 I have the pdp8/e *including* the console running on the Core
 6809 Board (plus one I/O Board)!  
 Nice!  I look forward to seeing this.

  If the HALT (or SING STEP) switch is down, you
can use the EXAM
 and DEP momentary switches.  If I press EXAM, I want to see the
 12-bit word contents of the address currently on display in the
 top row (memory address) of the console.
 That 12-bit word is displayed on the 12 lights below the memory
 address lights. Is it correct that the position of the selector
 switch (the rotary knob) must be on "AC" to see the contents of
 the active address?  Or is its position not relevant while HALT
 (or SING STEP) is active which seems odd to me because you want
 to be able to see more than just the AC when you HALTed the CPU?  
 The position is always relevant, but you don't set it to AC.  You set
 it to MD (Memory Data).  And when you press EXAM (or DEP), the address
 displayed on the upper row will increment (but the data displayed will
 remain the same, the data for the address that was current when you
 pressed EXAM/DEP).

  The answer seems easy, I just want to hear
confirmation.
 The current implementation shows the contents briefly after I
 pressed EXAM *and* the knob is on "AC".  Just *very briefly*,
 then the simulation shows the actual AC content again.  
 It shouldn't do that.

  So, on a real pdp8/e I assume that when the knob
is on "AC" you
 see the contents of AC when HALT is active?  
 Yes, without any glitches from the data.  But only if the rotary knob
 is turned to the AC position, otherwise you see whatever you've
 selected (STATE, STATUS, AC, MD, MQ, BUS).

  In that case, after the user pushed EXAM once 
(and the memory
 contents is displayed as I described above), how does he get to
 see contents of the "AC" again?

 Hope I made myself clear why I asked the question ...

 TIA,
 - Henk, PA8PDP.  
 -- 
 Pete						Peter Turnbull
 						Network Manager
 						University of York 