qmk_firmware/keyboards/tronguylabs/m122_3270/keymaps/default/readme.md

# Default keymap for m122-3270
This keymap is intended to make the PC/3270 122-key IBM keyboard work as closely as possible to the standard
PC/3270 keyboard's (part number 1397000) original mapping. Two layers are defined: layer 0 is the PC layout,
using the blue legends on the PC/3270 keys (as shipped by Unicomp; I don't have the original keycaps, and I
know there are a few differences), while layer 1 is the 3270 layout, with keycodes selected to make the `x3270`
suite do the right thing with each key as pressed. The idea here is, eventually, to get `x3270` to
automatically shift the keyboard to layer 1 when it gains focus.

When layer 0 is active, the upper left key of the 10-key pad is Escape, the Reset and Enter keys are Control, and
the comma and dot keys act like normal PC keys (< and >, repectively, when shifted). The Ctrl key (bottom right
of the left-side 10-key cluster) is always the left GUI key. PA2 and Jump/PA3 are PgUp and PgDn, respectively,
and the backtab key is End. The Rule/Home key is Home. The key next to the Escape key is Scroll Lock when unshifted,
and Num Lock when shifted.

When layer 1 is active, the keys do their labeled functions. The only keys that don't do anything are CrSel,
ExSel, and Jump, though only a few of the alternate functions (on the front of the keys) work: left/right/delete
word and PA3. The rest aren't emulated by x3270. Many of the keys that have function in PC mode will *not* have
that same function in 3270 mode, since x3270 uses different keystrokes to accomplish the same function.

To manually switch to layer 1, hold the Zoom key (the one on the far lower left of the keyboard) and press Clear
(the one at the top right of that same block of 10 keys); to switch back to layer 0, hold the Zoom key and hit
Attn (the one at the top left of that block of 10). Holding the Zoom key and the spacebar gets you to keys that
control QMK itself: Zoom-space-R resets to the bootloader, Zoom-space-E erases the EEPROM (which currently does
nothing), and Zoom-space-D turns the debugger on and off.

Note that you need to set your Linux system to use the Scroll Lock key as the Compose key in order to get the
cent sign to register as intended, and add the following lines to a file in your home directory named `.x3270pro`
to make Dup and Field Mark work:
```
x3270.keymap.m122: #override \
 Ctrl<Key>F: FieldMark()\n\
 Ctrl<Key>D: Dup()
```
You need to then invoke `x3270` with the parameter `-keymap m122` to activate those definitions.