Subject: Re: resurrecting a PDP-11/10

From: Andreas Freiherr <[email-masked]>
Date: Wed Mar 5 15:37:00 2003

Barry,

didn't you ask (under the pseudonym of Fred Feuerstein) for a 
description of the switches on a DS120 Terminal Controller?

I managed to find a user manual from the stone age, stating that the 
"Logic Card" is part number 512000-2. Not quite the 5120000-1 that you 
mention in your posting, but possibly close enough to provide hints for 
what functions might be there. YMMV...

This is what the manual says about the DIP switches:

SWITCH	FUNCTION
    1	Carriage motor disable (test only)
  * 2	Reverse channel override
  * 3	FDX/HDX override
  * 4	Local Auto-LF override
** 5	Parity odd (ON)  parity even (ON)
** 6	Parity enable (ON)  parity disable (OFF)
    7	AUTO-LF from line (ON)  disable (OFF)
** 8	X-on, X-off handshaking  enable (ON)  disable (OFF)

* On DECwriter models with the 8-key control pad, these switches are
   duplicated on the keyboard.  Those models with the 3 rocker-switch
   panel must control these features with the DIP-switches.

** See Appendix B, "Additional User Information", for a functional
    description of these switches.

End of cite. Appendix B talks a lot about half-duplex modes, which I 
presume will not be used with your PDP-11. Hence, you will want to have 
switches 2 & 3 in the OFF position.

The description of switch 5 obviously contains an error. For even 
parity, the switch needs to be in the OFF position (says appendix B).

Another noteworthy cite: "If parity is disabled by DIPswitch #6 "OFF", 
then DIPswitch #5 provides 8th bit spacing when "ON" and 8th bit marking 
when "OFF"."

In other words, you actually cannot select "no parity", but you can set 
"mark" or "space" parity.

You report having trouble with the 20mA interface. Maybe you need to 
switch from active to passive or vice versa? - Here's what the manual 
has about it:

3.1.3 20 MA CURRENT LOOP

A 20mA current loop interface is provided featuring a photo isolated 
receiver and transmitter. The receiver and transmitter may be configured 
to operate in either passive or active mode. Unless otherwise specified 
at the time of purchase, the DS120 comes configured with a passive 
transmitter and receiver. Although specified at 20 mA, the signal line 
currents flowing in the receiver loop may be as high as 80 mA without 
harming the interface. Any current in excess of 15 mA will be 
interpreted as a mark, and any current under 3 mA is interpreted as a 
space. 1500 volts of isolation is provided by the photo isolater if 
passive is employed.

The jumper configuration for the current loop interface is as follows:

            W1    W2    W3    W4    W5    W6    W7    W8   W13   W14
-------------------------------------------------------------------
PASSIVE   Out    In    In    In    In   Out   Out   Out   Out   Out
  ACTIVE    In   Out   Out   Out   Out    In    In    In    In    In

The connections for this interface are as follows:

    PIN  2: Transmit -
	3: Receive -
	5: Transmit +
	7: Receive +

End of cite. Hope this helps.

If you need more information, I can get whatever is printed in the 
manual for you. I do have a LA36, but it features the original DEC 
controller board, so I have no way of actually trying anything.

--
Andreas Freiherr
Vishay Semiconductor GmbH, Heilbronn, Germany
http://www.vishay.com

---

From: Gene Ehrich <[email-masked]>
Date: Wed Mar 5 16:08:01 2003

I received a solicitation for some software that caught my interest from 
gochange.net

I never heard of it and they want me to register before I can get in touch 
with the seller.

Does anybody here have any experience with this site/organization?

---

From: "Eric Smith" <[email-masked]>
Date: Wed Mar 5 17:04:01 2003

Gene wrote:
> I never heard of it and they want me to register before I can get in
> touch  with the seller.

Don't tell me you're actually considering doing business with a
spammer???  Ugh!