PC912XDP512F0MPVR datasheet(511/1348 Pages) FREESCALE

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Chapter 11 Serial Communication Interface (S12SCIV5)

MC9S12XDP512 Data Sheet, Rev. 2.21

Freescale Semiconductor

511

Enable single-wire operation by setting the LOOPS bit and the receiver source bit, RSRC, in SCI control

the RSRC bit connects the TXD pin to the receiver. Both the transmitter and receiver must be enabled

(TE = 1 and RE = 1).The TXDIR bit (SCISR2[1]) determines whether the TXD pin is going to be used as

an input (TXDIR = 0) or an output (TXDIR = 1) in this mode of operation.

NOTE

In single-wire operation data from the TXD pin is inverted if RXPOL is set.

11.4.8

Loop Operation

In loop operation the transmitter output goes to the receiver input. The RXD pin is disconnected from the

SCI.

Figure 11-31. Loop Operation (LOOPS = 1, RSRC = 0)

Enable loop operation by setting the LOOPS bit and clearing the RSRC bit in SCI control register 1

(SCICR1). Setting the LOOPS bit disables the path from the RXD pin to the receiver. Clearing the RSRC

bit connects the transmitter output to the receiver input. Both the transmitter and receiver must be enabled

(TE = 1 and RE = 1).

NOTE

In loop operation data from the transmitter is not recognized by the receiver

if RXPOL and TXPOL are not the same.

11.5

Initialization/Application Information

11.5.1

Reset Initialization

See Section 11.3.2, “Register Descriptions”.

11.5.2

Modes of Operation

11.5.2.1

Run Mode

Normal mode of operation.

To initialize a SCI transmission, see Section 11.4.5.2, “Character Transmission”.

RXD

Transmitter

Receiver

TXD

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