Preamble, Break, And Data Transmission Priority - Motorola DSP56305 User Manual

Serial Communication Interface (SCI)
Operating Modes
Operation starts as follows:
• For an internally generated clock, the SCLK signal starts operation immediately
after the SCI is enabled (Step 3 above) in Asynchronous modes. In Synchronous
mode, the SCLK signal is active only while transmitting (the clock is gated).
• Data is received only when the receiver is enabled (RE = 1) and after the SCI
receive sequence occurs on the RXD signal, as defined by the operating mode
(e.g., idle line sequence).
• Data is transmitted only after the transmitter is enabled (TE = 1), and after
transmitting the initialization sequence defined by the operating mode.
8.4.4

Preamble, Break, and Data Transmission Priority

More than one transmission command may be set at the same time:
1. Preamble (TE is set.)
2. Break (SBK is set or is cleared.)
3. Data for transmission available (TDRE is cleared.)
After the current character transmission, if two or more of these commands are set, the
transmitter executes them in the following order:
1. Preamble
2. Break
3. Data Available
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