MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
25-12 Freescale Semiconductor
25.4.3 Programmable MCKO Frequency
MCKO is an output clock to the development tools used for the timing of MSEO and MDO pin functions.
MCKO is derived from the system clock, and its frequency is determined by the value of the MCKO_DIV
field in the port configuration register (PCR) located in the NPC. Possible operating frequencies include
one-half, one-quarter, and one-eighth system clock speed.
Figure 25-7 shows the MCKO_DIV encodings. In this table, SYS_CLK represents the system clock
frequency. The default value selected if a reserved encoding is programmed is SYS_CLK/2.
25.4.4 Nexus Messaging
Most of the messages transmitted by the NDI include a SRC field. This field is used to identify which
source generated the message. Figure 25-8 shows the values used for the SRC field by the different clients
on the MPC5553/MPC5554. These 4-bit values are specific to the MPC5553/MPC5554. The same values
are used for the client select values written to the client select control register.
Table 25-6. NDI Configuration Options
JCOMP Asserted
MCKO_EN bit of the Port
Configuration Register
FPM bit of the Port
Configuration Register
Configuration
No X X Reset
Yes 0 X Disabled
Yes 1 1 Full-Port Mode
Yes 1 0 Reduced-Port Mode
Table 25-7. MCKO_DIV Values
MCKO_DIV[2:0] MCKO Frequency
0b000 SYSCLK – MPC5553 Only
Reserved – MPC5554 Only
0b001 SYS_CLK/2
0b010 Reserved
0b011 SYS_CLK/4
0b100 Reserved
0b101 Reserved
0b110 Reserved
0b111 SYS_CLK/8
Table 25-8. SRC Packet Encodings
SRC[3:0] Client
0b0000 e200z6
0b0001 eDMA
0b0010 eTPU1 (ENGINE1_SRC)
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