DSP56857 datasheet(311/662 Pages) FREESCALE

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Functional Description

Enhanced Synchronous Serial Interface (ESSI), Rev. 4

Freescale Semiconductor

12-11

If the Normal mode is configured to provide more than one time slot per frame, data is

transmitted only in the first time slot. No data is transmitted in subsequent time slots. Figure 12-2

and Figure 12-3 show sample timing of Normal mode transfers.

12.5.1.1 Normal Mode Transmit

Conditions for data transmission from the ESSI in the Normal mode:

1. Set the STXCR, SCR2, SCR3, and SCR4 registers to select Normal mode operation.

2. Define the transmit clock, transmit frame sync and frame structure required for proper

system operation.

3. ESSI enabled (ESSIEN = 1)

4. Enable TXFIFO (TFEN = 1) and configure the Transmit Watermark (TFWM = n) if this

TXFIFO is used.

5. Write data to the Transmit Data (STX) register.

6. Enable transmit interrupts.

7. Set the TE bit (TE = 1) to enable the transmitter on the next frame sync boundary.

Figure 12-2 and Table 12-6 describe the functions performed during transmit operation in this

mode.

Figure 12-2. Normal Mode Transmit Timing (WL=8 Bit Words, DC = 1)

Valid

Indefinite transition depends on SW interrupt processing

Invalid

SCK

SC2

STX register

TDE status bit / interrupt

TXSR register

STD

DSP56857 Datasheet(PDF) 311 Page - Freescale Semiconductor, Inc