MSC8144E Reference Manual, Rev. 3
20-22
Freescale
Semiconductor
UART
20.4 Modes of Operation
The following sections summarize the UART modes of operation.
20.4.1 Run Mode
Run mode is the normal mode of operation.
20.4.2 Single-Wire Operation
Normally, the UART (SCI) uses two signals for transmitting and receiving data. In single-wire
operation,
URXD
is disconnected from the UART and is available as a GPIO signal (see Chapter
22, GPIO). The UART uses
UTXD
for both receiving and transmitting data. Setting the data
direction bit for
UTXD
, SCIDDR[DDRTX], configures
UTXD
as the output for transmitted data.
Clearing the data direction bit, SCIDDR[DDRTX], disables the transmitter to drive
UTXD
.
Enable single-wire operation by setting the SCICR[LOOPS] bit and the receiver source bit,
SCICR[RSRC]. Setting the SCICR[LOOPS] bit disables the path from
URXD
to the receiver.
Setting the SCICR[RSRC] bit connects the receiver input to the output of
UTXD
. Both the
transmitter and receiver must be enabled (SCICR[TE] = 1 and SCICR[RE] = 1). You can
configure
UTXD
(see Chapter 22, GPIO) for full CMOS drive or for open-drain drive. The
configuration bit controls
UTXD
in both normal operation and single-wire operation. The
configuration bit also allows the
UTXD
outputs to be tied together in a multiple-transmitter
system, which allows the
UTXD
signals of nonactive transmitters to follow the logic level of an
active one. External pull-up resistors are necessary when using open-drain outputs.
Figure 20-19. Single-Wire Operation (LOOPS = 1, RSRC = 1)
UTXD
URXD
Transmitter
General-Purpose I/O
Receiver
SCIDDR[DDRTX]
GPIO
UART
Summary of Contents for MSC8144E
Page 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Page 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Page 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Page 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Page 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Page 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Page 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Page 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Page 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Page 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...