mc9s12xs128 Freescale Semiconductor, Inc, mc9s12xs128 Datasheet - Page 431

• Manufacturer Part Number: mc9s12xs128
• Description: Hcs12 Microcontrollers 16-bit Automotive Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Enable single-wire operation by setting the LOOPS bit and the receiver source bit, RSRC, in SCI control
register 1 (SCICR1). Setting the LOOPS bit disables the path from the RXD pin to the receiver. Setting
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.
14.4.8
In loop operation the transmitter output goes to the receiver input. The RXD pin is disconnected from the
SCI.
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).
14.5
14.5.1
See
14.5.2
14.5.2.1
Normal mode of operation.
To initialize a SCI transmission, see
Freescale Semiconductor
Section 14.3.2, “Register
Initialization/Application Information
Loop Operation
Reset Initialization
Modes of Operation
Run Mode
In single-wire operation data from the TXD pin is inverted if RXPOL is set.
In loop operation data from the transmitter is not recognized by the receiver
if RXPOL and TXPOL are not the same.
Figure 14-31. Loop Operation (LOOPS = 1, RSRC = 0)
Descriptions”.
S12XS Family Reference Manual, Rev. 1.10
Transmitter
Receiver
Section 14.4.5.2, “Character
NOTE
NOTE
Transmission”.
RXD
TXD
Serial Communication Interface (S12SCIV5)
431