Synchronous serial Re: E-Mail Formats RE: Future of cctalk/cctech

Peter Coghlan cctalk at
Thu Jun 18 08:06:15 CDT 2020

Antonio Carlini wrote:
> On 18/06/2020 10:06, Peter Coghlan via cctalk wrote:
> >
> > To get somewhere near back on topic, I am trying to set up a synchronous
> > serial link between two MicroVAX 3100 machines with DSH32 (or DST32 maybe)
> > interfaces.  One of the options I have is a BC19D cable and a BC19V cable
> > which seem to be identical or nearly identical.  Each plugs into a DSH32
> > at one end and has a V.24 DB25 connector at the other end.  I don't seem
> > to have anything available in the way of a pair of suitably similar modems
> > or a modem eliminator to put between the two V.24 connectors.  Can anyone
> > suggest some kind of a quick hardware hack that I could use to fill the
> > gap?  Is a pair of DB25 sockets with crossed over wiring betweeen them
> > sufficient or do I need something that generates clock signals too?
> >
> I can't find my DHS32/DST32 docs right now but it's probably a simple 
> re-spin of the DSH32.
> I think that the DST32 was the uVAX2000 option and the DSH32 was for the 
> uVAX 3100 series.
> My notes say that my MicroVAX 2000 has a DST32 (54-17230) but the 
> preliminary version of EK-283AA-AD-001 is for the DSH32 and that talks 
> about the MicroVAX 2000!

Thanks for your reply Antonio.

I have found the whole thing very confusing too.  My suspicion was also
that they were pretty much the same thing but the DST32 had exernal
connectors suitable for mounting in a MicroVAX 2000 while the DST32 had
external connectors that could be mounted in a MicroVAX 3100.  That is,
until I also came across the preliminary version of EK-283AA-AD-001
which threw cold water on that theory.  Unless it was originally called
the DSH32 and then renamed to DST32 for the MicroVAX 2000 or something...

The console code in one of my MicroVAX 3100 machines shows this:

>>> test 50

KA41-D  V1.0


   DSH32-A  00FF.0001  V1.0
   DSH32-S  0000.0001  V3.0
   NI       0000.0001

Yet in VAX/VMS 7.3, I see this:


OpenVMS (TM) VAX System analyzer

SDA> show dev zsa0

I/O data structures
ZSA0                                    ZS_DST32          UCB address: 814EAA40


> I think that in the lab at DEC I used a modem eliminator (I used to 
> support all of the synch devices supported by VAX WANDD). I may even 
> have some of those modem eliminators in the garage.

I was hoping to use VAX WANDD but I ended up having to install DECnet OSI
on VMS 7.3.  Perhaps if I dig up an earlier VMS version, I can avoid using

> Just to double check ... you definitely have synch boards and not (for 
> example) 8-way asynch lines? There were a whole bunch of designators 
> that were so very close: DST32, DHT32, DSH32, DHW41, DSW41!

I have two boards in two MicroVAX 3100 machines.  Each board has one
Synchronous serial port (50 pin D connector) and eight asynchronous
terminal lines (36 pin Centronics connector).  To add further confusion,
I have a third MicroVAX 3100 which has the 50 pin and 36 pin external
connectors on the back but no actual DSH32/DHT32 board inside!

I also have the following cables:

1   BC19C Rev B1  50 pin D (female) to 13/15 pin D (male) X.21
1   BC19D Rev B   50 pin D (female) to 16/25 pin D (male) V.24
1   BC19F Rev B   50 pin D (female) to 17/34 pin "square" thing (male) V.35
1   BC19V         50 pin D (female) to 16/25 pin D (male) V.24

and I also have two Nokia DS 60100 baseband modems, one with a V.35
interface card and one with an X.21 interface card.  When I hook up the
former with the BC19F cable, I can get the lights on the modem to react
when I try to access ZSA0: on the MicroVAX.  However, I can't get any
reaction when I use the BC19C cable with the latter even when I jumper
the modem to take account of the fewer signals available in X.21.  It
may be that the BC19C is meant for something other than the DSH/T32...
Anyway, this whole line of attack is fairly academic as the modems can
only do 48kbps - 160kbps and the maximum for the DSH/T32 seems to be

Peter Coghlan.

> Antonio

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