Clock Source; Operating Mode; Schematic Diagram Of The Clock Interface; Operating Mode Selection - Motorola 56F827 Hardware User Manual

2.5 Clock Source

The 56F827EVM uses a 4.00MHz crystal, Y1, connected to its External Crystal Inputs,
EXTAL and XTAL. The 56F827 uses its internal PLL to multiply the input frequency by
20, achieving its 80MHz maximum operating frequency. An external oscillator source can
be connected to the hybrid controller by using the oscillator bypass connectors, JG4 and
JG5; see Figure 2-4. If the input frequency is above 4MHz, then the EXTAL input should
be jumpered to ground by adding a jumper between JG4 pins 2 and 3. The input frequency
would then be injected on JG5's pin 2. If the hybrid 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.
Figure 2-4. Schematic Diagram of the Clock Interface

2.6 Operating Mode

The 56F827EVM provides a boot-up MODE selection jumper, JG6. This jumper is used
to select the operating mode of the hybrid controller as it exits RESET. Refer to the
DSP56F827 User's Manual for a complete description of the chip's operating modes.
shows the two operation modes available on the 56F827.
Table 2-3
Operating Mode
0
3
2-6
Freescale Semiconductor, Inc.
EXTERNAL
OSCILLATOR
HEADERS
JG4
3
2
1
4.00MHz
10M
JG5
1
2
12.2880MHz
3
Table 2-3. Operating Mode Selection
JG6
1–2
No Jumper
56F827 Evaluation Module Hardware User's Manual
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56F827
EXTAL
XTAL
Comment
Bootstrap from internal memory
Bootstrap from external memory
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