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CHAPTER 18 INTERRUPT FUNCTIONS AND TEST FUNCTIONS
(3) Key return mode register (KRM)
This register enables or disables releasing the standby mode by using the key return signal (detection of the
falling edge of port 4).
KRM is set by a 1-bit or 8-bit memory manipulation instruction.
This register is set to 02H when the RESET signal is input.
Figure 18-20. Format of Key Return Mode Register
Caution
Be sure to clear KRIF to 0 by program when using the falling edge detection of port 4. (This
bit is not automatically cleared by hardware).
18.5.2 Test input signal acceptance 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 signal
If a falling edge is input to a pin of port 4 (P40 to P47), an external test input signal (INTPT4) 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.
Symbol
KRM
0
0
0
0
0
0
KRMK KRIF
KRIF
0
1
Key return signal detection flag
Not detected
Detected (detection of falling edge of port 4)
FFF6H 02H R/W
Address On reset R/W
KRMK
0
1
Controls standby mode by key return signal
Enables releasing standby mode
Disables releasing standby mode
6
5
4
3
2
1
0
7