Conference 7.286::keyboard_design

260.0. "vt220 with LK401-AA okay?" by RHETT::SHEPPARD () Tue Feb 25 1997 12:39

[recently cross-posted to ATLANT::TERMINALS, note #3250]

Hello,
    A customer recently purchased LK401-AA RevH01 keyboards to upgrade
a number of old VT220 terminals from their original LK201 Rev-AC
keyboards. He now reports that when power-cycled all terminals now
come up again showing the error:
    keyboard error 04
I'm guessing this is an 'unrecognized keyboard' error or something similar.

He double-checked and says the LK201 keyboards still work just fine when
swapped in. Ergo, probably a compatibility issue.

So, two questions:
1. Will an LK401-AA RevH01 play properly with a vt220 ?

2. If not, can anyone shed some light on the physical/electrical interface
   to the LK201 and LK401 keyboards ?

   If the problem is as simple as a pinout-swap, the customer is
   willing to take a stab at fixing it himself -- with the proper info.

Thanks in advance for any pointers or information !


                        Steve Sheppard
                        Digital Unix / Ultrix Applications Support Team
                        sheppard@decatl.alf.dec.com

   The LK401 keyboard has a couple of new keys, I'd not expect it to be
   entirely compatible with the LK201.  Given the keyboard signalling
   used to communicate from the terminal to the keyboard over a serial
   connection, this involves rather more than soldering a wire or two.

   Those VT220 terminals are long past the standard depreciation and
   should be retired to pasture -- the customer will want to consider
   replacing them with a more recent terminal.  (Recent terminals in
   the VT-series use PC-compatible keyboards, with the PC layout, or
   with the DIGITAL LK4xx layout.)

Actually, LK401s first come up in LK201 mode and need a command to
switch into 401 mode.  An LK401 will work fine with a vt220 (I've
done it).