SCI Control Registers
1342
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Serial Communication Interface (SCI) Module
Table 26-5. SCI Global Control Register 1 (SCIGCR1) Field Descriptions (continued)
Bit
Field
Value
Description
16
LOOP BACK
Loopback bit. The self-checking option for the SCI can be selected with this bit. If the SCITX and
SCIRX pins are configured with SCI functionality, then the SCITX pin is internally connected to the
SCIRX pin. Externally, during loop back operation, the SCITX pin outputs a high value and the
SCIRX pin is in a high-impedance state. If this bit value is changed while the SCI is transmitting or
receiving data, errors may result.
0
Loop back mode is disabled.
1
Loop back mode is enabled.
15-10
Reserved
0
Reads return 0. Writes have no effect.
9
POWERDOWN
Power down. When the POWERDOWN bit is set, the SCI attempts to enter local low-power mode.
If the POWERDOWN bit is set while the receiver is actively receiving data and the wake-up
interrupt is enabled, then the SCI immediately asserts an error interrupt to prevent low-power mode
from being entered. Only Privilege mode writes allowed.
0
Normal operation.
1
Low-power mode is enabled.
8
SLEEP
SCI sleep. In a multiprocessor configuration, this bit controls the receive sleep function. Clearing
this bit brings the SCI out of sleep mode.
0
Sleep mode is disabled.
1
Sleep mode is enabled.
Note: The receiver still operates when the SLEEP bit is set; however, RXRDY is updated and
SCIRD is loaded with new data only when an address frame is detected. The remaining
receiver status flags (see
) are updated and an error interrupt is requested if the
corresponding interrupt enable bit is set, regardless of the value of the SLEEP bit. In this
way, if an error is detected on the receive data line while the SCI is asleep, software can
promptly deal with the error condition.
Note: The SLEEP bit is not automatically cleared when an address byte is detected.
See
for more information on using the SLEEP bit for multiprocessor communication.
7
SWnRST
Software reset (active low).
0
The SCI is in its reset state; no data will be transmitted or received. Writing a 0 to this bit initializes
the SCI state machines and operating flags as defined in
and
. All affected
logic is held in the reset state until a 1 is written to this bit.
1
The SCI is in its ready state; transmission and reception can be done. After this bit is set to 1, the
configuration of the module should not change.
Note: The SCI should only be configured while SWnRESET = 0.
6
Reserved
0
Reads return 0. Writes have no effect.
5
CLOCK
SCI internal clock enable. The CLOCK bit determines the source of the module clock on the
SCICLK pin.
0
The external SCICLK is the clock source.
1
The internal SCICLK is the clock source.
Note: If an external clock is selected, then the internal baud rate generator and baud rate
registers are bypassed. The maximum frequency allowed for an externally sourced SCI clock
is VCLK/16.
4
STOP
SCI number of stop bits per frame.
0
One stop bit is used.
1
Two stop bits are used.
Note: The receiver checks for only one stop bit. However in idle-line mode, the receiver
waits until the end of the second stop bit (if STOP = 1) to begin checking for an idle period
.
