Operation Panel - Panasonic KX-FT21RS Serivce Manual

6.11. OPERATION PANEL

The unit consists of an LCD (Liquid crystal display), KEYs, photo interrupters (sensor), and analog switches (for key scan).
The key scan (analog switch control, reading), sensor detection (sensor control, reading) and LCD control are all controlled by I/O
of ASIC (IC1) on the digital board.
6.11.1. KEY SCAN
When CN1(8) (OPSEL) is "H", the analog switch (IC1) is available. The "KLATCH", "KSCLK" and "KTXD" control the analog switch
(IC1) to read at KIN0~3.
Analog Switch (IC1) Control
KLATCH (A)
KSCLK (B)
ktxd (C)
Key Matrix
Fig. a
0 1 2
L H L
L L H
L L L
135
3 4 5
H L H
H L L
L H H
6 7
L H
H H
H H
KX-FT21RS