µPD6121, 6122
6. DOUBLE-INPUT OPERATION
All keys are provided with a multiple-input prevention circuit. When two or more keys are pressed simulta-
neously, no signal is transmitted; but when the keys K21 and K22, K21 and K23, or K21 and K24 are pressed
together, D5 is set to “1”. However, the way keys are pressed determines the priority: If K22/K23/K24 are pressed
126 ms or longer after K21 is pressed, transmission is performed in this mode.
Double-input key operation is ideally suited for tape recording error prevention applications.
Double-Input Operation Key Codes
KEY
D0
1
D1
0
D2
1
D3
0
D4
1
D5
1
D6
0
D7
0/1
0/1
0/1
K21 + K22
K21 + K23
K21 + K24
0
1
1
0
1
1
0
1
1
1
0
1
1
0
Double-Input Operation Timing
1 Double-input transmission
K21 code transmission
t > 126 ms
D5 + K22/K23/K24 code transmission
K21
push
K22/K23/K24
push
2 No operation
K21 code transmission
36 ms < t < 126 ms
Transmission stop
K21
push
K22/K23/K24
push
3 No operation
No transmission
K21
–36 ms < t < 36 ms
push
K22/K23/K24
push
4 No operation
K21
push
t > 126 ms
K22/K23/K24 code transmission
Transmission stop
K22/K23/K24
push
13
NEC [ NEC ]
