Test Input Signal Acknowledge Operation; Key Return Mode Register Format - NEC PD78052 User Manual

(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
The internal test input signal (INTWT) is generated with watch timer overflow, and the WTIF flag is set. If not
masked with bit 7 (WTMK) of interrupt mask flag register 1L (MK1L) at this time, a standby release signal is
generated. The watch function is available by checking the WTIF flag using a shorter cycle than the watch
timer overflow cycle.
(2) External test signal
When a falling edge (external test input signal) is input to the port 4 (P40 to P47) pins, KRIF is set. If not masked
with bit 1 (KRMK) of key return mode register (KRM) at this time, a standby release signal is generated. If
port 4 is used as key matrix return signal input, whether or not a key input has been applied can be checked
from the KRIF status.
CHAPTER 21 INTERRUPT AND TEST FUNCTIONS
Figure 21-21. Key Return Mode Register Format
4 3 2 <1> <0>
0 0 0 KRMK KRIF
When
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
509