MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 25-17
25.7 NPC Functional Description
25.7.1 NPC Reset Configuration
The NPC is placed in disabled mode upon exit of reset. If message transmission via the auxiliary port is
desired, a write to the PCR is then required to enable the NPC and select the mode of operation. Asserting
MCKO_EN places the NPC in enabled mode and enables MCKO. The frequency of MCKO is selected by
writing the MCKO_DIV field. Asserting or negating the FPM bit selects full-port or reduced-port mode,
respectively.
Table 25-12 describes the NPC reset configuration options.
29 MCKO_EN MCKO enable. Enables the MCKO clock. When enabled, the frequency of MCKO is
determined by the MCKO_DIV field.
0 MCKO clock is driven to zero.
1 MCKO clock is enabled.
28–26 MCKO_DIV
[2:0]
MCKO division factor. Determines the frequency of MCKO relative to the system clock
frequency when MCKO_EN is asserted. The table below shows the meaning of
MCKO_DIV values. In this table, SYS_CLK represents the system clock frequency.
25–1 — Reserved.
0 PSTAT_EN Processor status mode enable. Enables processor status (PSTAT) mode. In PSTAT mode,
all auxiliary output port MDO pins are used to transmit processor status information, and
Nexus messaging is unavailable.
0 PSTAT mode disabled
1 PSTAT mode enabled
Note: PSTAT mode is intended for factory processor debug only. The PSTAT_EN bit
should be written to disable PSTAT mode by the customer. No Nexus messages are
transmitted under any circumstances when PSTAT mode is enabled
Table 25-12. NPC Reset Configuration Options
JCOMP Asserted? PCR[MCKO_EN] PCR[FPM]
Configuration
No X X Reset
Yes 0 X Disabled
Table 25-11. PCR Field Descriptions (Continued)
Bits Name Description
MCKO_DIV[2:0] MCKO Frequency
0 SYS_CLK – MPC5553 Only
Reserved – MPC5554 Only
1 SYS_CLK/2
2 Reserved
3 SYS_CLK/4
4 Reserved
5 Reserved
6 Reserved
7 SYS_CLK/8
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