Friday, August 26, 2022

Entrex Data/Scopes (Nixdorf Keystations) spotted in Belgium on

My friend Dominique just shared these with me.  The story is:

"I also saw an ad for two Entrex terminals two month ago, 40km from my house [in Liedekerke], Unfortunately the person never answered me, It was strange because one of the two terminals was painted red (like in Knight Rider), I kept the pictures for you."
So, can we track down this seller, or these terminals?  We will certainly try, indeed!

It's a Belgian marketplace, but unfortunately the ad disappeared. I then found the person on facebook by cross-checking information but also no answers. From memory it was in the Antwerp region, in this situation, I can not tell you more alas. It was strange to see this ad anyway, like as a sign, because in fact I have never seen an Entrex terminals ad so close to my house"

At first, I thought that these *might* be the same two keystation/terminals sold in Germany back in March & April 2018, but a quick comparison of any of the tags on the inside shows that they are all completely different machines...  

Friday, August 5, 2022

Entrex 480/Nixdorf 620 Data/Scope Keystation (Terminal) Communication Protocol

sergiopl — Sept 3, 2022 at 3:56 AM
On a PC keyboard there is a tiny CPU that creates scan codes for each key, even shift. Then there is a 8051 or something known as keyboard controller that interpret that and send to PC CPU

In Mera/Entrex you only get scan codes generated from EPROM, mixed together with bit flags connected to modifier keys and that is shifted out of the device
All "meaning" of the keys is up to the host

ashlin4010 — Sept 3, 2022 at 4:03 AM
so how many bits are used for the code and flags? 8 and 2?

sergiopl — Sept 3, 2022 at 4:04 AM
6 bits are keyboard code
3 bits for control character (modifiers)
1 bit to indicate if key is a response to key press or to "read screen character" command
Rest is padding / framing
Those 3 bits are also messed up - they don't cover all possible combinations and some modifier combo has the same bit pattern 😆
If you open polish manual linked above there are two tables with those modifiers

Terminal Connector Pinout:

Similarities with the MERA-ELZAB 7951 terminal pinout:

sergiopl — Sept 6, 2022 at 5:11 PM
I think Entrex code also can be said slightly modified Manchester, but I'm not sure if that is really the case. It looks like except clock signal is not interleaved on each half of bit so this is a bit strange
This is also not a NRZ or NRZI code, also similar but not exact.
But in terms of non repeating sequences it matches definition of Manchester

sergiopl — Sept 6, 2022 at 5:13 PM

There you have it: 3270 controller board
Building an IBM 3270 terminal controller_Lobsters - MdEditor
Building an IBM 3270 terminal controller
This is Manchester encoding. As you can see "1" is sent as LoHi. "0" is HiLo
In our case "0" is LL if previous bit was "1", and HL if previous bit was also 0.
"1" is HH if previous bit was 0, LH if previous bit was 1
While it looks similar over the wire sampling point is different and encoding method is also different
But this approach simplifies decoding because you just need to sample at 3/4T and you are done.