Freescale Semiconductor MPC5675EVB, User Manual

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MPC5675EVB Users Manual Rev 2.0 July 2010
MPC5675EVB Page 4 of 29
3.2 MCU Clock Control
3.2.1 Main Clock Selection (J42, J43, J73 and J74)
The EVB supports three possible MCU clock sources:
(1) The local 40MHz oscillator circuit
(2) An 4MHz oscillator module on the EVB (U19), driving the MCU EXTAL signal
(3) An external clock input to the EVB via the SMA connector (J76), driving the MCU EXTAL
signal
The clock circuitry is shown in the diagram below. Please refer to the appropriate EVB schematic for
specific jumper numbers and circuitry.
Figure 3-4 EVB Clock Selection
Table 3-2 Clock Source Jumper Selection
Jumper Position PCB
Legend Description
J73 (U19 PWR)
FITTED (D) EVB oscillator module U19 is powered
REMOVED EVB oscillator module U19 is not
powered
J74 (OSC SEL)
1-2 (D) MOD 8Mhz Oscillator is routed from U19
2-3 SMA SMA external square wave input
J42
Must Match J43 1-2 (D) Y1 MCU Clock is Y1 XTALIN
2-3 GND GND
J43
Must Match J42
1-2 (D)
Y1 MCU Clock is Y1 XTALOUT
2-3 EVB MCU Clock is Selected by J74
Note that the 3.3V regulator must be enabled when using oscillator module Y1.
CAUTION
The MPC5675K clock circuitry is all 3.3v based. Any external clock signal driven into the SMA
connector must have a maximum voltage of 3.3V.
J73
SMA
(J76)
Oscillator
Module
(U19)
3.3V
Local Crystal
Circuit (Y1)
MCU
EXTAL
XTAL
J74
J43
J42
GND
EVB Clock Circuitry
1
1