DSP56857 datasheet(242/662 Pages) FREESCALE

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Functional Description

5685X Digital Signal Controller User Manual, Rev. 4

10-6

Freescale Semiconductor

10.6 Functional Description

Figure 10-1 explains the structure of the SCI module. The SCI allows full duplex, asynchronous,

NRZ serial communication between the DSC and remote devices, including other digital signal

controllers. The SCI transmitter and receiver operate independently, although they use the same

baud rate generator. The monitors the status of the SCI, writes the data to be transmitted, and

processes received data.

When initializing the SCI, be sure to set the proper peripheral enable bits in the GPIO registers as

well as any pull-up enables.

10.6.1 Data Frame Format

The SCI uses the standard Non-Return-to-Zero (NRZ) mark/space data frame format illustrated

in Figure 10-3.

Figure 10-3. SCI Data Frame Formats

Each data character is contained in a frame including a Start bit, eight or nine Data bits, and a

Stop bit. Clearing the M bit in the SCI Control Register (SCICR) configures the SCI for 8-bit data

characters. A frame with eight data bits has a total of 10 bits.

Setting the M bit configures the SCI for 9-bit data characters. A frame with nine data bits has a

total of 11 bits.

Table 10-4. Example 8-Bit Data Frame Formats

Start

Bit

Data

Bits

Address

Bit

Parity

Bit

Stop

Bit

18001

17011

1. The address bit identifies the frame as an address character.

Please see Section 10.6.4.8

Bit 5

Start

Bit

Bit 0

Bit 1

Stop

Bit

Start

Bit

9-Bit Data Format

Bit 2

Bit 3

Bit 4

Bit 6

Bit 7

Parity

or Data

Bit

Parity

or Data

Bit

Bit M in SCICR Set

8-Bit Data Format

Bit M in SCICR Clear

Bit 5

Bit 0

Bit 1

Bit 2

Bit 3

Bit 4

Bit 6

Bit 7

Bit 8

Stop

Bit

Start

Bit

Start

Bit

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