NXP Semiconductors MPC5644A, Reference Manual, Page: 1680 / 1735

Nexus Port Controller (NPC)
MPC5644A Microcontroller Reference Manual, Rev. 6
1680 Freescale Semiconductor
The PCR, shown in Figure 37-4 , is used to select the NPC mode of operation, enable MCKO and select
the MCKO frequency, and enable or disable MCKO gating. This register should be configured as soon as
the NPC is enabled.
The PCR register may be rewritten by the debug tool subsequent to the enabling of the NPC for low power
debug support. In this case, the debug tool may set and clear the LP_DBG and LPn_SYN bits, but must
preserve the original state of the remaining bits in the register.
NOTE
The mode or clock division must not be modified after MCKO has been
enabled. Changing the mode or clock division while MCKO is enabled can
produce unpredictable results.
Table 37-6. PCR field descriptions
Bit Name Description
31 FPM Full Port Mode
The value of the FPM bit determines if the auxiliary output port uses the full MDO port or a
reduced MDO port to transmit messages.
1 = All MDO pins are used to transmit messages
0 = A subset of MDO pins are used to transmit messages
30 MCKO_GT MCKO Clock Gating Control
This bit is used to enable or disable MCKO clock gating. If clock gating is enabled, the MCKO
clock is gated when the NPC is in enabled mode but not actively transmitting messages on the
auxiliary output port. When clock gating is disabled, MCKO is allowed to run even if no auxiliary
output port messages are being transmitted.
1 = MCKO gating is enabled
0 = MCKO gating is disabled
29 MCKO_EN MCKO Enable
This bit enables the MCKO clock to run. When enabled, the frequency of MCKO is determined
by the MCKO_DIV field.
1 = MCKO clock is enabled
0 = MCKO clock is driven to zero
28:2
6
MCKO_DIV MCKO Division Factor
The value of this signal determines the frequency of MCKO relative to the system clock
frequency when MCKO_EN is asserted.
Table 37-7 shows the meaning of MCKO_DIV Values.
In this table, SYS_CLK represents the system clock frequency.
25 EVT_EN EVTO/EVTI Enable
This bit enables the EVTO/EVTI port functions.
1 = EVTO/EVTI port enabled
0 = EVTO/EVTI port disabled
24 — Reserved
23 NEXCFG Nexus Configuration Select
Generic Nexus control bit. Function is device-specific.
1 = NEXCFG set
0 = NEXCFG cleared
22:1
6
— Reserved