em78p862a ELAN Microelectronics Corp, em78p862a Datasheet - Page 22

• Manufacturer Part Number: em78p862a
• Description: 8-bit Risc Type Microprocessor
• Manufacturer: ELAN Microelectronics Corp

EM78862B
8-Bit RISC Type Microprocessor
16 of 35
08.02.2004 (V1.0)
6.2.12 IOCE (Port9 GPIO/LCD Segment, Port6 GPIO/LCD Com,
6.2.12.1 Page 0 (Port9 GPIO/LCD Segment, Port6 GPIO/LCD Com, LCD Bias,
Bit 0: (SC) Scan key signal.
P9SH
Bit 7
0: Disable scan key signal
1: Enable scan key signal
Once you enable this bit, all of the LCD signal will have a low pulse during a common
period. This pulse has 30µs width. Use the following procedures to implement the key
scans function:
a) Set Port7 as input port
b) Set IOCD Page 0 Port 7 to pull high
c) Enable scan key signal
d) Once a key is pressed, set RA (6)=1, and switch to normal mode
e) Blank LCD. Disable scan key signal
f)
g) Set P9SH = 1, P9SL =1. Define Port 9 as LCD signal and enable LCD.
LCD Bias, Scan Key Signal, Port7 Open Drain, Counter 1/2 Clock
Source, Counter1 Pre-Scaler Control Register)
Scan Key Signal Control Register)
Set P9SL = 0, P9SH = 0. Port 9 sent probe signal to Port 7 and read Port 7 to get
the key.
performed.
Note that a probe signal instruction delay will occur before the next instruction is
P93
P92
P91
P90
P9SL
Bit 6
This procedure is also applicable to Port 6 and Port 8.
Bit 5
P6S
P73
Fig. 7 Key Scans Circuit
BIAS3
Bit 4
NOTE
P72
This specification is subject to change without further notice.
BIAS2
Bit 3
KEY5
P71
BIAS1
Bit 2
KEY1
KEY2
KEY3
KEY4
P70
Bit 1
0
Bit 0
SC