Reset Causes; Table 4.2A Reset Causes - Fujitsu F2MC-16LX MB90580 Series Hardware Manual

4.2 Reset Causes

4.2 Reset Causes
When a reset cause occurs, F
release of reset signal. A reset can be caused by the following factors:
Power-on reset
Hardware standby release
Watch-dog timer overflow
External reset request via RSTX pin
Reset request by software
Right after stop mode release or power on reset, the MCU will wait for the stabilization time before
resumption of any activities.
When reset occurs, F
The content of watchdog timer control register will change according to the reset cause. Thus, the cause of
previous reset can be known.
Note: While an external bus is used, the address generated by the device is undefined when
a reset cause occurs. All external bus access signals, including RDX and WRX,
become inactive.
Reset
Power-on
Hardware
standby
Watch-dog timer
External pin
Software
* In stop or hardware standby mode, a reset input allows for oscillation stabilization time regardless of the
reset cause.
* The oscillation stabilization time for a power-on reset is fixed to 2
types of reset, the oscillation stabilization wait time is determined by CS1 and CS0 of the clock selection
register.
As shown in Figure 4.2a, each reset cause has a corresponding flip-flop. The contents of the flip-flop can
be obtained by reading the watch-dog timer control register. If identifying the reset cause is required after
the reset is released, ensure that the value read from the watch-dog timer control register is processed by
software and processing branches to an appropriate program.
48 Chapter 4: Clock and Reset
2
MC-16LX terminates the currently executing processing and waits for the
2
MC-16LX will stop all operation at once and wait for the release of reset.

Table 4.2a Reset causes

Cause
When the power is turned
on
'L' level input to HSTX pin
Watch-dog timer overflow
'L' level input to RSTX pin
'0' written to RST bit of
STBYC
Machine clock Watch-dog timer
Main clock
Main clock
Main clock
Previous status Previous status
maintained maintained
Previous status Previous status
maintained maintained
18
cycles of source oscillation. For other
Oscillation
stabilization
wait
Stop Yes
Stop Yes
Stop Yes
No
No
MB90580 Series