PC312XDP512F0CFVR datasheet(497/1348 Pages) FREESCALE

497 / 1348 page

Chapter 11 Serial Communication Interface (S12SCIV5)

MC9S12XDP512 Data Sheet, Rev. 2.21

Freescale Semiconductor

497

11.4.5

Transmitter

Figure 11-16. Transmitter Block Diagram

11.4.5.1

Transmitter Character Length

The SCI transmitter can accommodate either 8-bit or 9-bit data characters. The state of the M bit in SCI

control register 1 (SCICR1) determines the length of data characters. When transmitting 9-bit data, bit T8

in SCI data register high (SCIDRH) is the ninth bit (bit 8).

11.4.5.2

Character Transmission

To transmit data, the MCU writes the data bits to the SCI data registers (SCIDRH/SCIDRL), which in turn

are transferred to the transmitter shift register. The transmit shift register then shifts a frame out through

the TXD pin, after it has prefaced them with a start bit and appended them with a stop bit. The SCI data

registers (SCIDRH and SCIDRL) are the write-only buffers between the internal data bus and the transmit

shift register.

76543210L

11-Bit Transmit Register

TIE

TDRE

TCIE

SBK

Parity

Generation

SCI Data Registers

Transmitter Control

Internal Bus

SBR12:SBR0

Baud Divider

÷ 16

Bus

Clock

SCTXD

TXPOL

LOOPS

LOOP

RSRC

CONTROL

To Receiver

Transmit

Collision Detect

TDRE IRQ

TC IRQ

SCTXD

SCRXD

(From Receiver)

TCIE

BERRIF

BER IRQ

BERRM[1:0]

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