HC705MC4GRSSLASHD datasheet(121/180 Pages) NXP

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Serial Communications Interface

SCI Data Format

General Release Specification

Serial Communications Interface

11.4 SCI Data Format

The SCI uses the standard nonreturn-to-zero mark/space data format

illustrated in Figure 11-1.

Figure 11-1. SCI Data Format

11.5 SCI Operation

The SCI allows full-duplex, asynchronous, RS232 or RS422 serial

communication between the MCU and remote devices, including other

MCUs. The transmitter and receiver of the SCI operate independently,

although they use the same baud-rate generator. The following

paragraphs describe the operation of the SCI transmitter and receiver.

11.5.1 Transmitter

Figure 11-2 shows the structure of the SCI transmitter.

11.5.1.1 Character Length

The transmitter can accommodate either 8-bit or 9-bit data. The state of

the M bit in SCI control register 1 (SCCR1) determines character length.

When transmitting 9-bit data, bit T8 in SCCR1 is the ninth bit (bit 8).

11.5.1.2 Character Transmission

During transmission, the transmit shift register shifts a character out to

the PB4/TDO pin. At this time, the SCI data register (SCDR) is the

write-only buffer between the internal data bus and the transmit shift

8-BIT DATA FORMAT

BIT M IN SCCR1 CLEAR

9-BIT DATA FORMAT

BIT M IN SCCR1 SET

START

BIT

BIT 0

BIT 1

BIT 2

BIT 3

BIT 4

BIT 5

BIT 6

BIT 7

BIT 8

STOP

BIT

START

BIT

BIT 0

BIT 1

BIT 2

BIT 3

BIT 4

BIT 5

BIT 6

BIT 7

START

BIT

STOP

BIT

START

BIT

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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