Section 19 Band-Gap Circuit, Power-On Reset, and Low-Voltage Detection Circuits
19.3.3
Deciding Reset Source
The source of a reset can be decided by reading the reset source decision register (LVDRF) in the
reset exception handler (see table 19.2). After that, writing 0 to the bit can clear the flag and can be
ready to decide the next reset source.
Figure 19.7 shows a timing of setting the bits in the register.
Table 19.2 Deciding Reset Source
LVDRF
PRST
WRST
Reset Source
1
0
0
0
0
1
Power-on reset or LVDR occurred
Reset signal input on external reset pin
WDT reset occurred
Power supply voltage
Internal reset signal
PRST bit
Set by
Set by temporary drop of
power supply voltage
power-on reset
Read and
cleared
(0 is written)
Read and
cleared
(0 is written)
Set by
WDT reset
Read and
cleared
(0 is written)
WRST bit
Figure 19.7 Timing of Setting Bits in Reset Source Decision Register
Rev. 3.00 Sep. 10, 2007 Page 392 of 528
REJ09B0216-0300
RENESAS [ RENESAS TECHNOLOGY CORP ]
