EM78815
8-Bit Microcontroller
The key scan waveform is as follows.
K ey scan pin(P8,P9)
V D D
GN D
30us
Fig.21 Keyscan Waveform
Bit 5 (KEYSTRB) : Key strobe enable control bit
0/1 → disable/enable
Key strobe signal , if you set this bit , the segment will switch to strobe signal
temporally and output a zero signal ( one instruction long ) one by one from Port 80 to
Port 87 and Port 90 to Port 97. During one strobe time, the CPU will check whether
Port 7 (0:3) is equal to "1111" or not. If not, the CPU will latch a zero at RB Page 1
and RC Page 1 one by one depending on which segment strobe. After strobe, this bit
will be cleared. Fig. 22 is a key strobe signal.
One instruction
REGISTER
RB(0)
RB(1)
RB(2)
RB(3)
RB(4) RB(5)
RB(6)
RB(7) RC(0)
RC(1) RC(2) RC(3) RC(4) RC(5) RC(6)
RC(7)
STROBE
PORT80
PORT81
PORT82
PORT83
PORT84
PORT85
PORT86
PORT87
PORT90
PORT91
PORT92
PORT93
PORT94
PORT95
PORT96
PORT97
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
Fig.22 Key strobe Signal
44 •
Product Specification (V2.4) 02.17.2006
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
