mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 272

• Manufacturer Part Number: mc9s12e256
• Description: Hcs12 Microcontrollers 16-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 8 Serial Communication Interface (SCIV4)
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
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).
8.5
This section describes the interrupt originated by the SCI block.The MCU must service the interrupt
requests.
272
Interrupt
.
TDRE
RDRF
IDLE
OR
TC
Table 8-17
Interrupts
Loop Operation
SCISR1[7]
SCISR1[6]
SCISR1[5]
SCISR1[3]
SCISR1[4]
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.
Source
lists the five interrupt sources of the SCI.
Figure 8-25. Loop Operation (LOOPS = 1, RSRC = 0)
Local Enable
TCIE
ILIE
RIE
TIE
TRANSMITTER
RECEIVER
Table 8-17. SCI Interrupt Sources
MC9S12E256 Data Sheet, Rev. 1.08
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.
occurred.
Active high level. Indicates that receiver input has become idle.
Active high level. This interrupt indicates that an overrun condition has
NOTE
NOTE
RXD
TXD
Description
Freescale Semiconductor