Motorola DSP56305 User Manual page 304

Enhanced Synchronous Serial Interface (ESSI)
Operating Modes
Notes: 1. The order of the steps is optional except that the interrupt trigger
configuration must not be completed until the ISR configuration has been
completed. Since 2c may cause an immediate transmit without generating
an interrupt, the transmit data preload in 2b should be performed before 2c
to ensure valid data is sent in the first transmission.
2. After the first transmit, subsequent transmit values are typically loaded
into TXnn by the ISR (one value per register per interrupt). Therefore, if N
items are to be sent from a particular TXnn, the ISR will need to load the
transmit register (N – 1) times.
3. Steps 2c and 2d may be performed using a single instruction.
4. If an interrupt trigger event occurs at a time when not all interrupt trigger
configuration steps have been performed, the event will be ignored forever
(the event will not be queued in this case).
5. If interrupts derived from the core or other peripherals need to be enabled
at the same time as ESSI interrupts, step 2f should be done last.
7-46 DSP56305 User's Manual MOTOROLA