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(3) Key return mode register (KRM)
This register set the standby mode clear enable/disable with the key return signal (falling edge detection of Port
4).
KRM is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets KRM to 02H.
Symbol
KRM
Caution
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18.5.2 Test input signal acknowledge operation
(1) Internal test input signal
An internal test input signal (INTWT) is generated when the watch timer overflows and the WTIF flag is set by
it. At this time, the standby release signal is generated if it is not masked by the interrupt mask flag (WTMK).
By checking the WTIF flag in a cycle shorter than the overflow cycle of the watch timer, the watch function can
be effected.
(2) External test input signal
If a falling edge is input to a pin of port 4 (P40 to P47), an external test input signal (INTP4) is generated, setting
the KRIF flag. At this time, the standby release signal is generated if it is not masked by the interrupt mask flag
(KRMK). By using port 4 for key return signal input of a key matrix, the presence or absence of a key input can
be checked by the status of the KRIF flag.
CHAPTER 18 INTERRUPT FUNCTIONS AND TEST FUNCTION
Figure 18-20. Key Return Mode Register Format
7
6
5
4
0
0
0
0
When falling edge detection is used in Port 4, take care to clear KRIF to 0 (KRIF is not automatically
cleared to 0).
3
2
<1>
<0>
0
0
KRMK
KRIF
KRMK
Address
When Reset
R/W
FFF6H
02H
R/W
KRIF
Key return signal detection flag
0
Non detection
1
Detection (falling edge detection of Port 4)
Standby mode control with key return signal
0
Standby mode clear enabled
1
Standby mode clear disabled
471
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