DEC VT220 Technical Manual page 154

•
KEYBOARD
10
(firmware)
Keycode 01 (decimal),
01 (hexadecimal)
•
KEYBOARD
10
(hardware)
Keycode 00 (decimal),
00 (hexadec imal)
•
KEY DOWN ON POWER-UP ERROR CODE Keycode 61 (decimal),
3D (hexadecimal)
•
POWER-UP SELF-TEST ERROR CODE
Keycode 62 (decimal) ,
3E (hexadec ima I)
KEYBOARD
10
is a two byte identification code, transmitted
after the power-up self-test (refer to section 7.5.4.3). It is
also sent on request from the system module (refer to section
7.5.5.3).
KEY DOWN ON POWER-UP ERROR CODE
pressed on power-up.
indicates that a key was
POWER-UP SELF-TEST ERROR CODE -- indicates to the system module
that the ROM or RAM self-test of the system module failed (refer
to section 7.5.4.3).
7.5.4.3 Power-Up Transmission Upon power-up, the keyboard
performs a self-test in less than 70 ms, then transmits the
self-test results to the system module in 4 bytes.
Byte 1
Byte 2
KBYD (firmware) This is the keyboard
identification (ID) stored in the firmware.
KBID (hardware) This is the keyboard
10
read from hardware jumpers.
Byte 3 ERROR Two error codes indicate
failure of the ROM or RAM self-test
processor (3E hexadecimal), or a
powerup (3D hexadecimal) • No
indicated by 00.
either the
within the
keydown on
error is
Byte 4 KEYCODE This byte contains the first
keycode detected if there was a key pressed on
power-up. No error is indicated by 00.
If the ROM self-test (CHECKSUM) fails and the error is critical,
the keyboard is unable to transmit. Noncritical errors let the
keyboard continue operating.
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