The TRAB keyboard implementation is similar to that for LWMON and
R360MPI boards. The only difference concerns key naming. There are 4
keys on TRAB: 1, 2, 3, 4.

1) The "kbd" command provides information about the current state of
   the keys. For example,

	TRAB # kbd
	Keys: 1 0 1 0

   means that keys 1 and 3 are pressed. The keyboard status is also
   stored in the "keybd" environment variable. In this example we get

	keybd=1010

2) The "preboot" variable is set according to current environment
   settings and keys pressed. This is an example:

	TRAB # setenv magic_keys XY
	TRAB # setenv key_magicX 12
	TRAB # setenv key_cmdX echo ## Keys 1 + 2 pressed ##\;echo
	TRAB # setenv key_magicY 13
	TRAB # setenv key_cmdY echo ## Keys 1 + 3 pressed ##\;echo

   Here "magic_keys=XY" means that the "key_magicX" and "key_magicY"
   variables will be checked for a match. Each variable "key_magic*"
   defines a set of keys. In the our example, if keys 1 and 3 are
   pressed during reset, then "key_magicY" matches, so the "preboot"
   variable will be set to the contents of "key_cmdY":

	preboot=echo ## Keys 1 + 3 pressed ##;echo

3) The TRAB board has optional modem support. When a certain key
   combination is pressed on the keyboard at power-on, the firmware
   performs the necessary initialization of the modem and allows for
   dial-in. The key combination is specified in the
   "include/configs/trab.h" file. For example:

	#define        CONFIG_MODEM_KEY_MAGIC  "23"

   means that modem will be initialized if and only if both keys 2, 3
   are pressed. Note that the format of this string is similar to the
   format of "key_magic*" environment variables described above.