Chapter 13 Key Return Circuit; Key Return Circuit Function; Key Return Circuit Configuration And Operation - NEC PD789860 User Manual

13.1 Key Return Circuit Function

In STOP mode, this circuit generates a key return interrupt (INTKR1) by inputting a P40/KR10 to P43/KR13 falling
edge.
Cautions 1. The key return interrupt is a non-maskable interrupt that is effective only in STOP mode. In
addition, P40/KR10 to P43/KR13 key input cannot be performed by mask control.
2. The key return signal cannot be detected even if a falling edge is generated on the other key
return pins while even one of the key return pins (P40/KR10 to P43/KR13) is low.

13.2 Key Return Circuit Configuration and Operation

Figure 13-1 shows the block diagram of the key return circuit. Figure 13-2 shows the generation timing of the key
return interrupt (INTKR1).
P40/KR10
P41/KR11
P42/KR12
P43/KR13
STOP signal
P4n/KR1n
INTKR1
Remark n = 0 to 3

CHAPTER 13 KEY RETURN CIRCUIT

Figure 13-1. Block Diagram of Key Return Circuit
Falling edge detector
STOP mode
Figure 13-2. Generation Timing of Key Return Interrupt
User's Manual U14826EJ5V0UD
Key return interrupt
(INTKR1)
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