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CHAPTER 21 RESET FUNCTION
User’s Manual U19780EJ2V0UD
561
21.1 Register for Confirming Reset Source
Many internal reset generation sources exist in the 78K0/Kx2-A microcontrollers. The reset control flag register
(RESF) is used to store which source has generated the reset request.
RESF can be read by an 8-bit memory manipulation instruction.
RESET input, reset by power-on-clear (POC) circuit, and reading RESF set RESF to 00H.
Figure 21-5. Format of Reset Control Flag Register (RESF)
Address: FFACH After reset: 00H
Note
R
Symbol
7 6 5 4 3 2 1 0
RESF
0 0 0
WDTRF
0 0 0
LVIRF
WDTRF
Internal reset request by watchdog timer (WDT)
0
Internal reset request is not generated, or RESF is cleared.
1
Internal reset request is generated.
LVIRF
Internal reset request by low-voltage detector (LVI)
0
Internal reset request is not generated, or RESF is cleared.
1
Internal reset request is generated.
Note
The value after reset varies depending on the reset source.
Caution Do not read data by a 1-bit memory manipulation instruction.
The status of RESF when a reset request is generated is shown in Table 21-3.
Table 21-3. RESF Status When Reset Request Is Generated
Reset Source
Flag
RESET Input
Reset by POC
Reset by WDT
Reset by LVI
WDTRF Set
(1)
Held
LVIRF
Cleared (0)
Cleared (0)
Held Set
(1)