15.8.3 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.
15.8.4 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.
15.8.4.1 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)
15.8.5 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
15.8.5.1 Clock Stop Mode
The clock stop mode supports the SPI master-slave protocol. If you do not plan to use the SPI protocol, you can
clear CLKSTP to disable the clock stop mode.
In the clock stop mode, the clock stops at the end of each data transfer. At the beginning of each data
transfer, the clock starts immediately (CLKSTP = 10b) or after a half-cycle delay (CLKSTP = 11b). The CLKXP
bit determines whether the starting edge of the clock on the MCLKX pin is rising or falling. The CLKRP bit
determines whether receive data is sampled on the rising or falling edge of the clock shown on the MCLKR pin.
summarizes the impact of CLKSTP, CLKXP, and CLKRP on serial port operation. In the clock stop
mode, the receive clock is tied internally to the transmit clock, and the receive frame-synchronization signal is
tied internally to the transmit frame-synchronization signal.
Multichannel Buffered Serial Port (McBSP)
940
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
Copyright © 2022 Texas Instruments Incorporated
Содержание TMS320 2806 Series
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