Clock Source; Operating Mode; Schematic Diagram Of The Clock Interface; Operating Mode Selection - Motorola DSP56852 User Manual

2.5 Clock Source

The DSP56852EVM uses a 4.00MHz crystal, Y1, connected to its External Crystal Inputs,
EXTAL and XTAL. To achieve its 120MHz maximum operating frequency, the
DSP56852 uses its internal PLL to multiply the input frequency by 30. An external
oscillator source can be connected to the DSP by using the oscillator bypass connectors,
JG3 and JG4; see Figure
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 DSP needs to be
synchronized to the codec's sample frequency, then the DSP'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 2-5. Schematic Diagram of the Clock Interface

2.6 Operating Mode

The DSP56852EVM provides a boot-up MODE selection switch, S5. This switch is used
to select the operating mode of the DSP as it exits RESET. Refer to the DSP56852 User's
Manual for a complete description of the chip's operating modes.
two operation modes available on the DSP56852.
Operating Mode
0
1
2
3
MOTOROLA
Freescale Semiconductor, Inc.
2-5. If the input frequency is above 4MHz, then the EXTAL
EXTERNAL
OSCILLATOR
HEADERS
JG4
3
2
1
4.00MHz
JG3
1
2
12.2880MHz
3
Table 2-3. Operating Mode Selection
S5 (ON)
1–2, 3-4 & 5-6 Bootstrap from External byte-wide memory
3-4 & 5-6 Bootstrap from SPI
1-2 & 5-6 Normal Expanded mode
5-6 Development Expanded mode
Technical Summary
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DSP56852
EXTAL
XTAL
Table 2-3
Comment
Operating Mode
shows the
2-7