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Nexus Port Controller (NPC)
37.5
Functional description
37.5.1
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 37-8
describes the NPC reset configuration options.
JCOMP equal to
npc_jcomp_plug?
no
yes
yes
yes
37.5.2
Auxiliary output port
The auxiliary output port is shared by each of the Nexus modules on the device. The NPC communicates
with each of the Nexus modules and arbitrates for access to the port.
37.5.2.1
Output message protocol
The protocol for transmitting messages via the auxiliary port is accomplished with the MSEO functions.
The MSEO pins are used to signal the end of variable-length packets and the end of messages. They are
not required to indicate the end of fixed-length packets. MDO and MSEO are sampled on the rising edge
of MCKO.
Figure 37-5
illustrates the state diagram for MSEO transfers. All transitions not included in the figure are
reserved, and must not be used.
1682
Table 37-8. NPC reset configuration options
MCKO_EN bit of the Port
Configuration Register
X
0
1
1
MPC5644A Microcontroller Reference Manual, Rev. 6
FPM bit of the Port
Configuration Register
X
X
1
0
Configuration
Reset
Disabled
Full-Port Mode
Reduced-Port Mode
Freescale Semiconductor
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