EM78860
8-BIT MICRO-CONTROLLER
7
6
5
P6S
4
3
2
1
0
0
SC
P9SH
P9SL
Bias3
Bias2
Bias1
• Bit 0 :SC (SCAN KEY signal ) 0/1 = disable/enable. Once you enable this bit , all of the LCD signal will have
a low pulse during a common period. This pulse has 30us width. Please use the procedure to implement the
key scan function.
a. set port7 as input port
b. set IOCD page0 port7 pull high
c. enable scan key signal
d. Once push a key . Set RA(6)=1 and switch to normal mode.
e. Blank LCD. Disable scan key signal.
f. Set P6S =0. Port6 sent probe signal to port7 and read port7. Get the key.
g. Note!! A probe signal should be delay a instruction at least to another probe signal.
h. Set P6S =1. Port6 as LCD signal. Enable LCD.
KEY5
KEY1
P63
P62
KEY2
KEY3
KEY4
P61
P60
P73
P72
P71
P70
Fig.8. Key scan circuit
VDD
V1
V2
V3
com2
V4
VLCD
GND
VDD
V1
V2
V3
V4
seg
VLCD
GND
30µs
Fig.9. Key scan signal
* This specification are subject to be changed without notice.
6.24.1998 11
ELAN [ ELAN MICROELECTRONICS CORP ]
