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CHAPTER 7 RESETS
7.5 Reset Cause Bits
A reset cause can be identified by reading the watchdog timer control register (WDTC).
■ Reset Cause Bits
As shown in Figure 7.5-1 , a flip-flop is associated with each reset cause. The contents of the flip-flops are
obtained by reading the watchdog timer control register (WDTC). If the cause of a reset must be identified
after the reset has been cleared, the value read from the WDTC should be processed by the software and a
branch made to the appropriate program.
Figure 7.5-1 Block Diagram of Reset Cause Bits
RST=L
SR
F/F
Q
SR
F/F
Q
SR
F/F
Q
SR
F/F
Q
: Set
: Flip Flop
: Reset
: Output
For MB90F367/T(S)
MB90367/T(S)
Failure of main/
sub clock
Clock
supervisor
Watchdog timer
control register
(WDTC)
RST pin
No periodic clear
No periodic clear RST bit set
Write detection
circuit of LPMCR,
RST bits
Watchdog timer
reset generation
detection circuit
Power-on
Power-on
generation
detection circuit
External reset
request detection
circuit
Drop power
supply voltage
Low voltage
detection circuit
CPU operation
detection reset
request detetion
circuit
Clear
Delay
circuit
Read watchdog
timer control
register (WDTC)
Internal data bus
T-suffix only
S
R
Q
F/F