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2.4.4.7
Flash standby reset
The flash standby reset is an internal factor reset generated by the reading or writing of data of the flash
memory while it is on standby.
Refer to "Flash Memory".
2.4.4.8
Internal factor reset detection status register
By reading the internal factor reset detection status register IRSTSR after the release of an internal factor
reset, except the power-on reset, the factor which causes a reset can be detected.
The internal factor reset detection status register is initialized by an external reset input or power-on re-
set.
Set IRSTSR<FCLR> to "1" and write 0x71 to SYSCR4. This enables IRSTSR<FCLR> and the internal
factor reset detection status register is clear to "0". IRSTSR<FCLR> is cleared to "0" automatically after
initializing the internal factor reset detection status register.
Note 1: Care must be taken in system designing since the IRSTSR may not fulfill its functions due to disturbing
noise and other effects.
Note 2: After IRSTSR<FCLR> is modified, SYSCR4 should be written 0x71 (Enable code for IRSTSR<FCLR>
in NORMAL mode when fcgck is fc/4 (CGCR<FCGCKSEL>=00). Otherwise, IRSTSR<FCLR> may be
enabled at unexpected timing.
2.4.4.9
How to use the external reset input pin as a port
To use the external reset input pin as a port, keep the external reset input pin at the "H" level until the power
is turned on and the warm-up operation that follows reset release is finished.
After the warm-up operation that follows reset release is finished, set P1PU0 to "1" and P1CR0 to "0", and
connect a pull-up resistor for a port. Then set SYSCR3<RSTDIS> to "1" and write 0xB2 to SYSCR4. This
disables the external reset function and makes the external reset input pin usable as a normal port.
To use the pin as an external reset pin when it is used as a port, set P1PU0 to "1" and P1CR0 to "0" and
connect the pull-up resistor to put the pin to the input mode. Then clear SYSCR3<RSTDIS> to "0" and write
0xB2 to SYSCR4. This enables the external reset function and makes the pin usable as the external reset input
pin.
Note 1: If you switch the external reset input pin to a port or switch the pin used as a port to the external reset
input pin, do it when the pin is stabilized at the "H" level. Switching the pin function when the "L" level is
input may cause a reset.
Note 2: If the external reset input is used as a port, the statement which clears SYSCR3<RSTDIS> to "0" is not
written in a program. By the abnormal execution of program, the external reset input set as a port may
be changed as the external reset input at unexpected timing.
Note 3: After SYSCR3<RSTDIS> is modified, SYSCR4 should be written 0xB2 (Enable code for
SYSCR3<RSTDIS>) in NORMAL1 mode when fcgck is fc/4 (CGCR<FCGCKSEL>=00). Otherwise,
SYSCR3<RSTDIS> may be enabled at unexpected timing.
TMP89FH42
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RA004