Transmitter Configuration
1099
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Multichannel Buffered Serial Port (McBSP)
transmit register. The DMA PERINTFLG is edge-sensitive and will fail to recognize the XRDY, which is
continuously high.
For more details about McBSP reset conditions and effects, see
,
Resetting and Initializing
a McBSP
.
15.9.3 Set the Transmitter Pins to Operate as McBSP Pins
To configure a pin for its McBSP function , you should configure the bits of the GPxMUXn register
appropriately. In addition to this, bits 12 and 13 of the PCR register must be set to 0. These bits are
defined as reserved.
15.9.4 Enable/Disable the Digital Loopback Mode
The DLB bit determines whether the digital loopback mode is on. DLB is described in
.
Table 15-48. Register Bit Used to Enable/Disable the Digital Loopback Mode
Register
Bit
Name
Function
Type
Reset
Value
SPCR1
15
DLB
Digital loopback mode
R/W
0
DLB = 0
Digital loopback mode is disabled.
DLB = 1
Digital loopback mode is enabled.
15.9.4.1 Digital Loopback Mode
In the digital loopback mode, the receive signals are connected internally through multiplexers to the
corresponding transmit signals, as shown in
. This mode allows testing of serial port code with
a single DSP device; the McBSP receives the data it transmits.
Table 15-49. Receive Signals Connected to Transmit Signals in Digital Loopback Mode
This Receive Signal
Is Fed Internally by
This Transmit Signal
DR (receive data)
DX (transmit data)
FSR (receive frame synchronization)
FSX (transmit frame synchronization)
MCLKR (receive clock)
CLKX (transmit clock)
15.9.5 Enable/Disable the Clock Stop Mode
The CLKSTP bits determine whether the clock stop mode is on. CLKSTP is described in
Table 15-50. Register Bits Used to Enable/Disable the Clock Stop Mode
Register
Bit
Name
Function
Type
Reset
Value
SPCR1
12-11
CLKSTP
Clock stop mode
R/W
00
CLKSTP = 0Xb
Clock stop mode disabled; normal clocking for
non-SPI mode.
CLKSTP = 10b
Clock stop mode enabled without clock delay
CLKSTP = 11b
Clock stop mode enabled with clock delay