Re: 5251/Twin-Ax terminal emulation

I have to say the USB twinax that TwinData sells are super easy to
install/use.

Jerry

On 12/3/2019 9:27 AM, Jason Olson wrote:

Personally I don't know why you would go through all this effort. It's
pretty easy to pick up some 5250 ISA and PCI cards off eBay, and connect

to

an older system that way. I still have a few terminals at home that I

use,

but I also have a 5250 PCMCIA card in my IBM T60 Thinkpad that I use the
most. I was able to grab 4 of these off eBay about 10 years ago.

So besides the technical hey I did this kinda thing, what are you trying

to

accomplish here?


Thanks,

Jason E. Olson
IBM i Engineer/Developer
josys36@xxxxxxxxx
480.223.2952


On Mon, Dec 2, 2019 at 9:33 AM <alan@xxxxxxxxxxx> wrote:

All,

I've built a line-sniffer for my mid-80s System/36 (5362) in an attempt
to fully understand the TwinAx electrical and protocol layers. The long
term goal is to build an affordable open-source terminal emulator
providing either a TN5250 bridge to emulated TwinAx terminal sessions or
a more simple telnet/ASCII/vt10x translation on a series of TCP ports by
a WiFi ESP32. twindata.com offers a lot of similar products but they
are closed-source and far outside of the price range of most retro
computing enthusiasts. There doesn't appear to be a lot of people
running older System/32, S/34, S/38 and gen-1 AS/400s. But the keyboard
pirates are slowly destroying older terminals and I want the surviving
machines to be easy to interface to so they can be as usable as
possible.

I've worked through all the electrical and framing issues and annotated
a few dumps of the S/36 IPL with both an InfoWindow II and 3179
attached. The output of which can be found here:

https://www.retrotronics.org/tmp/s36_ipl_decodes1_01dec19.zip

The message structure and limited command descriptions came from this
document starting on PDF page 122 / printed page number 4-9:

http://bitsavers.trailing-edge.com/pdf/ibm/5250_5251/SY31-0461-0_5251_Display_Station_Model_11_Maintenance_Information_Dec77.pdf

However it is incomplete. Not all commands are enumerated, the modifier
address bits are not explained (addresses a LU inside the terminal), and
none of the context or arguments for the commands are elaborated on. A
simple example of what I am referring to is, for example, the
explanation of the argument bits for the SET MODE command, etc.

Can anyone point me to a document or resource that fully explains the
TwinAx 5251 model 12 display protocol? I've been searching for days now
and no luck. And I really can't make anymore progress until I'm
unblocked by documentation. I simply don't have enough time to
trial-and-error reverse engineer bit meanings.

Thanks,

Alan Hightower
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Jerry Draper, Trilobyte Software Systems, since 1976
IBMi, Network, and Connectivity Specialists, LAN/WAN/VPN
Representing WinTronix, Synapse, HiT, and others .....
(415) 457-3431 opt-1 . www.trilosoft.com

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