Receiver Configuration
1134
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Multichannel Buffered Serial Port (McBSP)
15.8.22 Set the SRG Input Clock Polarity
Table 15-46. Register Bits Used to Set the SRG Input Clock Polarity
Register
Bit
Name
Function
Type
Reset
Value
PCR
1
CLKXP
MCLKX pin polarity
R/W
0
CLKXP determines the input clock polarity when the MCLKX pin
supplies the input clock (SCLKME = 1 and CLKSM = 1).
CLKXP = 0
Rising edge on MCLKX pin generates transitions
on CLKG and FSG.
CLKXP = 1
Falling edge on MCLKX pin generates transitions
on CLKG and FSG.
PCR
0
CLKRP
MCLKR pin polarity
R/W
0
CLKRP determines the input clock polarity when the MCLKR pin
supplies the input clock (SCLKME = 1 and CLKSM = 0).
CLKRP = 0
Falling edge on MCLKR pin generates transitions
on CLKG and FSG.
CLKRP = 1
Rising edge on MCLKR pin generates transitions
on CLKG and FSG.
15.8.22.1 Using CLKXP/CLKRP to Choose an Input Clock Polarity
The sample rate generator can produce a clock signal (CLKG) and a frame-synchronization signal (FSG)
for use by the receiver, the transmitter, or both. To produce CLKG and FSG, the sample rate generator
must be driven by an input clock signal derived from the CPU clock or from an external clock on the CLKX
or MCLKR pin. If you use a pin, choose a polarity for that pin by using the appropriate polarity bit (CLKXP
for the MCLKX pin, CLKRP for the MCLKR pin). The polarity determines whether the rising or falling edge
of the input clock generates transitions on CLKG and FSG.
15.9 Transmitter Configuration
To configure the McBSP transmitter, perform the following procedure:
1. Place the McBSP/transmitter in reset (see
).
2. Program the McBSP registers for the desired transmitter operation (see
).
3. Take the transmitter out of reset (see
15.9.1 Programming the McBSP Registers for the Desired Transmitter Operation
The following is a list of important tasks to be performed when you are configuring the McBSP transmitter.
Each task corresponds to one or more McBSP register bit fields.
•
Global behavior:
–
Set the transmitter pins to operate as McBSP pins.
–
Enable/disable the digital loopback mode.
–
Enable/disable the clock stop mode.
–
Enable/disable transmit multichannel selection.
•
Data behavior:
–
Choose 1 or 2 phases for the transmit frame.
–
Set the transmit word length(s).
–
Set the transmit frame length.
–
Enable/disable the transmit frame-synchronization ignore function.
–
Set the transmit companding mode.
–
Set the transmit data delay.