System Interface Unit (SIU)
MPC5553/MPC5554 Microcontroller Reference Manual,
Rev. 5
6-10
Freescale Semiconductor
6.3.1.2
Reset Status Register (SIU_RSR)
The SIU_RSR reflects the most recent source, or sources of reset, and the state of the configuration pins
at the time the reset occurred. This register contains one bit for each reset condition that can generate a
reset: power-on reset (POR), external, software system, software external reset, watchdog, loss of PLL
lock, loss of clock, or checkstop reset. A reset status bit that is set to 1 indicates that the last interrupt
request caused a reset. After the bit is set, the reset source status bits in the SIU_RSR remain set until
another reset occurs. In the following situations, more than one reset bit is set:
•
If a power-on reset request has negated resulting in the MPC5553/MPC5554 in reset, and an
external reset is requested, both the power-on and external reset status bits are set. In this case, the
MPC5553/MPC5554 started the reset sequence due to a power-on reset request, but ended the reset
sequence after an external reset request.
•
If a software external reset is requested, the SERF flag bit is set, but no previously set bits in the
SIU_RSR are cleared. The SERF bit is cleared by writing a 1 (write 1 to clear) to the bit location
or when another reset source is asserted.
•
If any of the loss-of-clock, loss-of-lock, watchdog, or checkstop reset requests occur on the same
clock cycle, and a higher priority reset source is not requesting reset (see
), the reset status
bits for all of the requesting resets are set.
Simultaneous reset requests are prioritized. When reset requests of different priorities occur on the same
clock cycle, the lower priority reset request is ignored. Only the highest priority reset request's status bit is
set. Except for a power-on reset request or writing a 1 to the SERF bit, all reset requests of any priority are
ignored until the MPC5553/MPC5554 exits reset.
Table 6-4. SIU_MIDR Field Descriptions (continued)
Register Bits
Field Name
Description
0–15
PARTNUM
MCU part number. Read-only, mask programmed part identification number of the
MCU. Reads 0x00 for the MPC5554. For the MPC5553 the value is 0x53.
16–23
Reserved.
24–27
MASKNUM_MAJOR
Major revision number of MCU mask. Read-only, mask programmed mask number of
the MCU. Reads 0x0 for the initial mask set of the MPC5554 and the MPC5553, and
changes sequentially for each mask set.
28–31
MASKNUM_MINOR
Minor revision number of MCU mask. Read-only, mask programmed mask number of
the MCU. Reads 0x0 for the initial mask set of the MPC5554 and the MPC5553, and
changes sequentially for each mask set.
Table 6-5. Reset Source Priorities
Reset Source
Priority
Power-on reset (POR) and external reset (Group 0)
Highest
Software system reset (Group 1)
Next highest (< Highest & > Next lowest)
Loss of clock, loss of lock, watchdog, checkstop (Group 2)
Next lowest ( > Lowest & < Next highest)
Software external reset (Group 3)
Lowest
Summary of Contents for MPC5553
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