PDP 11/03

Noel Chiappa jnc at mercury.lcs.mit.edu
Mon Nov 9 16:57:07 CST 2015

    > From: Jim Stephensn

    >> I can supply both null-modem and non-null-modem cable diagrams (for
    >> DB25 connectors, already worked out; I have made DB9 serial cables,
    >> but not for direct connection to a DLV11, but could generate those
    >> too).

    > I'd love that

OK, here are the bits.

For the 40-pin Berg/DuPont male header, when looking at the _header_ (on the
board) face-on, component-side up, pin A is in the lower left corner; they
then follow the 'DEC Alphabet' (What, you don't have this memorized? For
working with DEC gear, it's mandatory: 'ABCDEFHJKLMNPRSTUVWXYZ' - G, I, O and
Q are dropped), and then repeated, AA-VV.

For the 40-pin connector (M7800 DL11, M7940 DLV11):

 A - Ground
 B - Ground
 E - Interlock IN
 F - EIA Serial Output
 J - EIA Serial Input
 M - EIA Interlock OUT

So for a 'normal' serial cable (i.e. DTE, male DB25), connect J to pin 3, and
F to 2. For a 'null modem' serial cable (i.e. DCE, female DB25), connect J to
pin 2, and F to pin 3. Grounds connect to pins 1/7. Pin E must be connected
to M. For other signals, consult the DL11 User's Manual (DEC-11-HDLAA-B-D),
it has a full table.

For the 10-pin header, when looking at the _header_ face-on, component-side
up, pin 1 is in the upper right corner; pin 6 is missing (interlock), and 10
is in the lower left.
For the 10-pin connector (M8043 DLV11-J, M8189 11/23+, M8190 11/83-84):

 1 - Clock input
 2 - Ground
 3 - Transmit +
 4 - Transmit -
 5 - Ground
 6 - Index
 7 - Receive -
 8 - Receive +
 9 - Ground
 10 - +12V

It's set up to do either differential, or single-sided; the usual EIA usage
is to ground the - side of the received data, so you can run single-sided. So
for a cable _with_ null modem (i.e. DCE, to a female DB25), you want to

Header		DB25		Signal

 2		7		Ground
 3		3		Transmit Data
 7  Loopback IN
 8		2		Receive Data
 9  Loopback OUT

For a normal DTE cable (to male DB25), swap pins 2 and 3 on the DB25 in
the list above.

I don't have notes for the cables to a DB9, to connect up directly to a PC's
serial input port, but if you want, they are pretty easy to put together a
list for.

(I did make a female-female DB9-DB9 cable, with null modem built in, to test
my serial line program, so I have the pinout for those too - just no PDP-11
direct to PC cables; I had a stack of DB25 to DB9 adaptors that I bought on
eBait, and I wanted all my PDP-11 cables wired to DB25's, so I'd be able to
interconnect -11's easily.)


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