NEC mPD789026 Subseries, User Manual

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CHAPTER 10 INTERRUPT FUNCTIONS
User's Manual U11919EJ3V0UM00
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(5) Key return mode register 00 (KRM00)
KRM00 is used to specify the pin at which a key return signal is detected.
KRM00 is set with a 1-bit or 8-bit memory manipulation instruction.
Bit 0 (KRM000) is set for the four pins from KR0/P40 to KR3/P43. Bits 4 to 7 (KRM004 to KRM007) are set
in 1-bit units for pins KR4/P44 to KR7/P47, respectively.
RESET input clears KRM00 to 00H.
Figure 10-6. Key Return Mode Register 00 Format
KRM00n
0
1
Key Return Signal Detection Selection
Undetected
Detected (at the falling edge of port 4)
KRM007 KRM006 KRM005 KRM004 0 0 0 KRM000 KRM00
Symbol Address After Reset R/W
FFF5H 00H R/W
7 6 5 4 3 2 1 0
Cautions 1. Be sure to set bits 1 to 3 to 0.
2. When KRM00 is set to 1, the corresponding pin is connected to a pull-up resistor
unless it is in output mode. In output mode, the pull-up resistor is not connected.
3. Before setting KRM00, set bit 0 of MK1 (KRMK00 = 1) to disable interrupts.
To enable interrupts, clear bit 0 of IF1 (KRIF00 = 0), then bit 0 of MK1 (KRMK00 = 0).
Remark n = 0, 4 to 7
Figure 10-7. Falling Edge Detection Circuit
P40/KR0
P41/KR1
P42/KR2
P43/KR3
P44/KR4
P45/KR5
P46/KR6
P47/KR7
Selector
Note
Falling Edge
Detection Circuit
KRMK00
KRIF00 Set Signal
Standby Release Signal
Key Return Mode Register (KRM00)
Note Selector used to select the pin to be used for falling edge input