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MPC555
/
MPC556
RESET
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
7-6
7.5 Reset Configuration
7.5.1 Hard Reset Configuration
When a hard reset event occurs, the MPC555 / MPC556 reconfigures its hardware
system as well as the development port configuration The logical value of the bits that
determine its initial mode of operation, are sampled from the following:
• The external data bus pins DATA[0:31]
• An internal default constant (0x0000 0000)
• An internal NVM register value (CMFCFIG)
If at the sampling time (at HRESET negation) RSTCONF is asserted, then the config-
uration is sampled from the data bus. If RSTCONF is negated and a valid NVM value
exists (CMFCFIG bit HC=0), then the configuration is sampled from the NVM register
in the CMF module. If RSTCONF is negated and no valid NVM value exists (CMFCFIG
bit HC=1), then the configuration word is sampled from the internal default. HC will be
“1” if the internal flash is erased.
summarizes the reset configuration op-
tions.
NOTE
If the CMFCFIG reset config word is being used, then the flash is au-
tomatically enabled.
9
ILBC
Illegal bit change. This bit is set when the MPC555
/
MPC556 changes any of the following bits
when they are locked:
LPM[0:1], locked by the LPML bit
MF[0:11], locked by the MFPDL bit
DIVF[0:4], locked by the MFPDL bit
10
GPOR
Glitch detected on PORESET pin. This bit is set when the PORESET pin is asserted for more
than TBD ns
0 = No glitch was detected on the PORESET pin
1 = A glitch was detected on the PORESET pin
11
GHRST
Glitch detected on HRESET pin. This bit is set when the HRESET pin is asserted for more than
TBD ns
0 = No glitch was detected on the HRESET pin
1 = A glitch was detected on the HRESET pin
12
GSRST
Glitch detected on SRESET pin. If the SRESET pin is asserted for more than TBD ns the GHRST
bit will be set. If an internal or external SRESET is generated the SRESET pin is asserted and
the GSRST bit will be set. The GSRST bit remains set until software clears it. The GSRST bit
can be negated by writing a one to GSRST. A write of zero has no effect on this bit.
0 = No glitch was detected on SRESET pin
1 = A glitch was detected on SRESET pin
.
13:15
—
Reserved
NOTES:
1. In the USIU RSR, if both EHRS and ESRS are set, the reset source is internal. The EHRS and ESRS bits in RSR
register are set for any internal reset source in addition to external HRESET and external SRESET events. If both
internal and external indicator bits are set, then the reset source is internal.
Table 7-3 Reset Status Register Bit Descriptions (Continued)
Bit(s)
Name
Description
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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