All Ups - DEC VT220 Technical Manual

Both the keyclick and bell may be independently set to one of the
following eight volume levels.
000
highest
001
010 default
011
100
101
110
I I I -- lowest
7.5.3.2 Indicators (LEOs) -- The system module normally transmits
indicator control commands. However the following are exceptions.
•
•
7.5.4
Upon powerup, the keyboard turns all LEOs off.
After receiving the inhibit transmission command, the
keyboard turns on the keyboard-locked LED. The LEO is
turned off after the keyboard receives a resume
transmission command.
Keyboard-to-System Module Protocol
This section describes the keyboard-to-system module protocol.
7.5.4.1 Keycode Transmission The keyboard transmits single
byte keycodes that reflect the keyboard matrix status. The
eight-bit codes above 6410 are used for keycodes. Every key is
identified by a unique keycode. There are no special codes for
shifted or control keys.
Refer to Figure 7-7 and Tables 7-1 and 7-2 for complete keycode
matrix translation table information.
7.5.4.2 Special Code Transmission -- There are 13 special codes.
Nine codes have values above 6410 and four codes have values
below.
The following nine special codes have values above 6410 (keycode
value range).
•
•
•
ALL UPS
METRONOME CODE
OUTPUT ERROR
7-26
Keycode
179
(decimal),
B3 (hexadecimal)
Keycode 180 (decimal),
B4 (hexadecimal)
keycode 181 (decimal),
B5 (hexadecimal)