NEC PD78058FY(A) - Manual (Page 504)

504
CHAPTER 21 INTERRUPT AND TEST FUNCTIONS
7
0
Symbol
KRM
6
0
5
0
4
0
3
0
2
0
1
KRMK
0
KRIF
Address
FFF6H 02H
After
Reset
R/W
R/W
0
1
Key Return Signal
Not detected
Detected (port 4 falling edge detection)
KRIF
0
1
Standby Mode Control by Key Return Signal
Standby mode release enabled
Standby mode release disabled
KRMK
(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.
Figure 21-21. Key Return Mode Register Format
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.