Clock Source
Technical Summary, Rev. 3
Freescale Semiconductor
2-7
2.5 Clock Source
The 56858EVM uses a 4.00MHz crystal, Y1, connected to its external crystal inputs, EXTAL
and XTAL. To achieve its 120MHz maximum operating frequency, the 56858 uses its internal
PLL to multiply the input frequency by 30. An external oscillator source can be connected to the
controller by using the oscillator bypass connectors, JG3 and JG4; see
Figure 2-5
. If the input
frequency is above 4MHz, then the EXTAL input should be jumpered to ground by adding a
jumper between JG4 pins 1 and 2. The input frequency would then be injected on JG3’s pin 2. If
the controller needs to be synchronized to the codec’s sample frequency, then the controller’s
input frequency should be jumpered using the 12.2280MHz codec frequency. If the input
frequency is below 4MHz, then the input frequency can be injected on JG4’s pin 2.
56858
EXTERNAL
OSCILLATOR
HEADERS
JG4
3
2
1
1
2
3
EXTAL
XTAL
JG3
4.00MHz
12.2880MHz
+1.65V
Figure 2-5. Schematic Diagram of the Clock Interface
Содержание 56858
Страница 2: ......
Страница 6: ...DSP56858EVM User Manual Rev 3 iv Freescale Semiconductor ...
Страница 8: ...DSP56858EVM User Manual Rev 3 vi Freescale Semiconductor ...
Страница 40: ...DSP56858EVM User Manual Rev 3 2 24 Freescale Semiconductor ...
Страница 41: ...56858EVM Schematics Rev 3 Freescale Semiconductor Appendix A 1 Appendix A 56858EVM Schematics ...
Страница 59: ......