DEC VT220 Technical Manual page 127

CHAPTER 7
KEYBOARD (LK201)
7.1 INTRODUCTION
The LK201 keyboard module (shaded area in Figure 7-1) is the
user's interface to the terminal. The keyboard detects keystrokes,
encodes them, and transmits and receives information to and from
the CPU logic in the system box.
Communication between the keyboard and the CPU logic is
fUll-duplex, serial, and asynchronous at 4800 bits per second
(bps). The communication lines conform to EIA standard RS-423,
which applies to imbalanced voltage interfaces.
AC
INPlJT
'--,....-,.1
MONiTOR
Clf<;U ITS
PS ANO
MONITOR
BOARD
LOGIC
BOARD
'CONNECTOR PHYSICALL Y 'AQUNTED ON
PS AND MONITOR BOARD
Figure 7-1 VT220 Series Terminal
Functional Block Diagram
7-1