Motorola DSP56305 User Manual page 301

Here is an example of initializing the ESSI.
1. Put the ESSI in its individual reset state by clearing the PCR bits.
2. Configure the Control Registers (CRA, CRB) to set the operating mode. Disable
the transmitters and receiver by clearing the TE[2:0] and RE bits. Set the interrupt
enable bits for the operating mode chosen.
3. Enable the ESSI by setting the PCR bits to activate the input/output signals to be
used.
4. Write initial data to the transmitters which will be in use during operation. This
step is needed even if DMA is used to service the transmitters.
5. Enable the transmitters and receiver to be used.
Now the ESSI can be serviced by polling, interrupts, or DMA.
Once the ESSI has been enabled (Step 3), operation will start as follows:
• For internally generated clock and frame sync, these signals will start activity
immediate after the ESSI is enabled.
• Data will be received by the ESSI after the occurrence of a frame sync signal
(either internally or externally generated) only when the Receive Enable (RE) bit
is set.
• Data will be transmitted after the occurrence of a frame sync signal (either
internally or externally generated) only when the Transmitter Enable (TE[2:0]) bit
is set.
MOTOROLA
Enhanced Synchronous Serial Interface (ESSI)
DSP56305 User's Manual
Operating Modes
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