User guide

MPC5668EVB Users Manual Rev 0.1 May 2009
MPC5668EVBUM/D Page 10 of 29
3.2.2 32Khz External Clock Selection (J67 and J71)
The EVB also supports an external 32KHz watch crystal that can be used as a timing source within the MCU.
The 32Khz crystal can be optionally connected to PA[14] and PA[15] of the MCU. When using the 32KHz
crystal PA[14] and PA[15] will not be visible on P17 Port A header.
Figure 3-6 EVB Clock Selection
Table 3-6 32Khz Crystal Jumper Selection
Jumper
Position
PCB
Legend
Description
J67
Must Match J71
1-2
(
D)
Y3 32Khz Crystal (Y2) is connected to MCU
2-3 PA[14] Pin functions as Normal I/O
J71
Must Match J67
1-2
(D)
Y3 32Khz Crystal (Y2) is connected to MCU
2-3
PA[15]
Pin functions as Normal I/O
32Khz Crystal
Circuit (Y3)
MCU
EXTAL32 / PA[14]
XTAL32 / PA[15]
J67
J71
32KHz EVB Clock Circuitry
1
1
PA[14]
PA[15]