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(3) Key return mode register (KRM)
This register is used to set enable/disable of standby function clear by key return signal (port 4 falling edge
detection).
KRM is set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets KRM to 02H.
Symbol
7
6
5
KRM
0
0
0
Caution When port 4 falling edge detection is used, be sure to clear KRIF to 0 (not cleared to 0
automatically)
21.5.2 Test input signal acknowledge operation
(1) Internal test signal (INTWT)
When the clock timer overflows, a internal test input signal (INTWT) is generated, and this causes the WTIF
flag to be set. At this time, a standby release signal is generated if not masked by an interrupt mask flag
(WTMK). If the WTIF flag is checked for a shorter period than the clock timer's overflow period, the clock
function can be realized.
(2) External test signal (INTPT4)
When the falling edge is input to the pins of port 4 (P40 to P47), an external test input signal (INTPT4) is
generated, and this causes the KRIF flag to be set. At this time, a standby release signal is generated if not
masked by an interrupt mask flag (KRMK). By using port 4 as the key matrix key return signal input, it can
be checked if there was key input or not by the status of the KRIF flag.
504
CHAPTER 21 INTERRUPT AND TEST FUNCTIONS
Figure 21-21. Key Return Mode Register Format
4
3
2
1
0
0
0
0
KRMK
KRIF
After
Address
Reset
FFF6H
02H
KRIF
Key Return Signal
0
Not detected
1
Detected (port 4 falling edge detection)
KRMK
Standby Mode Control by Key Return Signal
0
Standby mode release enabled
1
Standby mode release disabled
R/W
R/W
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