MC9S12NE64_06 Datasheet, PDF (258/554 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 8 Serial Communication Interface (SCIV3)
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.
8.4.7 Loop Operation
In loop operation the transmitter output goes to the receiver input. The RXD pin is disconnected from the
SCI
.
TRANSMITTER
TXD
RECEIVER
RXD
Figure 8-25. 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).
8.5 Interrupts
This section describes the interrupt originated by the SCI block.The MCU must service the interrupt
requests. Table 8-17 lists the five interrupt sources of the SCI.
Table 8-17. SCI Interrupt Sources
Interrupt
TDRE
Source
SCISR1[7]
TC
RDRF
SCISR1[6]
SCISR1[5]
OR
IDLE
SCISR1[3]
SCISR1[4]
Local Enable
TIE
TCIE
RIE
ILIE
Description
Active high level. Indicates that a byte was
transferred from SCIDRH/L to the transmit
shift register.
Active high level. Indicates that a transmit is
complete.
Active high level. The RDRF interrupt indicates
that received data is available in the SCI data
register.
Active high level. This interrupt indicates that
an overrun condition has occurred.
Active high level. Indicates that receiver input
has become idle.
8.5.1 Description of Interrupt Operation
The SCI only originates interrupt requests. The following is a description of how the SCI makes a request
and how the MCU should acknowledge that request. The interrupt vector offset and interrupt number are
MC9S12NE64 Data Sheet, Rev. 1.1
258
Freescale Semiconductor