Chapter 5 Resets, Interrupts, and System Configuration
5.9.2
System Reset Status Register (SRS)
This register includes read-only status flags to indicate the source of the most recent reset. When a debug
host forces reset by writing 1 to BDFR in the SBDFR register, none of the status bits in SRS will be set.
Writing any value to this register address clears the COP watchdog timer without affecting the contents of
this register. The reset state of these bits depends on what caused the MCU to reset.
7
6
5
4
3
2
1
0
R
W
POR
PIN
COP
ILOP
Reserved
ICG
LVD
0
Writing any value to SIMRS address clears COP watchdog timer.
POR
LVR:
1
U
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
0
0
0
(1)
(1)
(1)
(1)
Any other
reset:
U = Unaffected by reset
1
Any of these reset sources that are active at the time of reset will cause the corresponding bit(s) to be set; bits corresponding
to sources that are not active at the time of reset will be cleared.
Figure 5-3. System Reset Status (SRS)
Table 5-4. SRS Register Field Descriptions
Field
Description
7
POR
Power-On Reset — Reset was caused by the power-on detection logic. Because the internal supply voltage was
ramping up at the time, the low-voltage reset (LVR) status bit is also set to indicate that the reset occurred while
the internal supply was below the LVR threshold.
0 Reset not caused by POR.
1 POR caused reset.
6
PIN
External Reset Pin — Reset was caused by an active-low level on the external reset pin.
0 Reset not caused by external reset pin.
1 Reset came from external reset pin.
5
COP
Computer Operating Properly (COP) Watchdog — Reset was caused by the COP watchdog timer timing out.
This reset source may be blocked by COPE = 0.
0 Reset not caused by COP timeout.
1 Reset caused by COP timeout.
4
Illegal Opcode — Reset was caused by an attempt to execute an unimplemented or illegal opcode. The STOP
instruction is considered illegal if stop is disabled by STOPE = 0 in the SOPT register. The BGND instruction is
considered illegal if active background mode is disabled by ENBDM = 0 in the BDCSC register.
0 Reset not caused by an illegal opcode.
ILOP
1 Reset caused by an illegal opcode.
MC9S08AC60 Series Data Sheet, Rev. 2
74
Freescale Semiconductor
FREESCALE [ Freescale ]
