Receiver Configuration
1126
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Multichannel Buffered Serial Port (McBSP)
Table 15-36. Register Bits Used to Set the Receive Frame Synchronization Mode (continued)
Register
Bit
Name
Function
Type
Reset
Value
SRGR2
15
GSYNC
Sample rate generator clock synchronization mode
R/W
0
If the sample rate generator creates a frame-synchronization signal
(FSG) that is derived from an external input clock, the GSYNC bit
determines whether FSG is kept synchronized with pulses on the FSR
pin.
GSYNC = 0
No clock synchronization is used: CLKG
oscillates without adjustment, and FSG pulses
every (FPER + 1) CLKG cycles.
GSYNC = 1
Clock synchronization is used. When a pulse is
detected on the FSR pin:
• CLKG is adjusted as necessary so that it is
synchronized with the input clock on the
MCLKR pin.
• FSG pulses FSG only pulses in response
to a pulse on the FSR pin. The frame-
synchronization period defined in FPER is
ignored.
For more details, see
Synchronizing Sample Rate Generator Outputs
to an External Clock
.
SPCR1
15
DLB
Digital loopback mode
R/W
0
DLB = 0
Digital loopback mode is disabled.
DLB = 1
Digital loopback mode is enabled. The receive
signals, including the receive frame-
synchronization signal, are connected internally
through multiplexers to the corresponding
transmit signals.
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.
The internal receive clock signal (MCLKR) and
the internal receive frame-synchronization signal
(FSR) are internally connected to their transmit
counterparts, CLKX and FSX.
CLKSTP = 11b
Clock stop mode enabled with clock delay. The
internal receive clock signal (MCLKR) and the
internal receive frame-synchronization signal
(FSR) are internally connected to their transmit
counterparts, CLKX and FSX.
Table 15-37. Select Sources to Provide the Receive Frame-Synchronization Signal and the Effect
on the FSR Pin
DLB
FSRM
GSYNC
Source of Receive Frame
Synchronization
FSR Pin Status
0
0
0 or 1
An external frame-synchronization signal
enters the McBSP through the FSR pin.
The signal is then inverted as determined
by FSRP before being used as internal
FSR.
Input
0
1
0
Internal FSR is driven by the sample rate
generator frame-synchronization signal
(FSG).
Output. FSG is inverted as determined by
FSRP before being driven out on the
FSR pin.
0
1
1
Internal FSR is driven by the sample rate
generator frame-synchronization signal
(FSG).
Input. The external frame-synchronization
input on the FSR pin is used to
synchronize CLKG and generate FSG
pulses.
1
0
0
Internal FSX drives internal FSR.
High impedance