Datasheet

Resets and Interrupts
Resets
MC68HC908GR8 — Rev 4.0 Technical Data
MOTOROLA Resets and Interrupts 65
4.3.4 SIM Reset Status Register
This read-only register contains flags to show reset sources. All flag bits
are automatically cleared following a read of the register. Reset service
can read the SIM reset status register to clear the register after power-
on reset and to determine the source of any subsequent reset.
The register is initialized on powerup as shown with the POR bit set and
all other bits cleared. During a POR or any other internal reset, the RST
pin is pulled low. After the pin is released, it will be sampled 32 XCLK
cycles later. If the pin is not above a V
IH
at that time, then the PIN bit in
the SRSR may be set in addition to whatever other bits are set.
NOTE: Only a read of the SIM reset status register clears all reset flags. After
multiple resets from different sources without reading the register,
multiple flags remain set.
POR — Power-On Reset Flag
1 = Power-on reset since last read of SRSR
0 = Read of SRSR since last power-on reset
PIN — External Reset Flag
1 = External reset via RST pin since last read of SRSR
0 = POR or read of SRSR since last external reset
COP — Computer Operating Properly Reset Bit
1 = Last reset caused by timeout of COP counter
0 = POR or read of SRSR
Address: $FE01
Bit 7654321Bit 0
Read: POR PIN COP ILOP ILAD 0 LVI 0
Write:
POR:10000000
= Unimplemented
Figure 4-3. SIM Reset Status Register (SRSR)
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
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