FSG
CLKG
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Frame-synchronization pulse width: (FWID + 1) x CLKG
Frame-synchronization period: (FPER+1) x CLKG
Receiver Configuration
1092
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Multichannel Buffered Serial Port (McBSP)
Table 15-39. Register Bits Used to Set the SRG Frame-Synchronization Period and Pulse
Width (continued)
Register
Bit
Name
Function
Type
Reset Value
Range for (FWID + 1):
1 to 256 CLKG cycles
Figure 15-49. Frame of Period 16 CLKG Periods and Active Width of 2 CLKG Periods
When the sample rate generator comes out of reset, FSG is in its inactive state. Then, when GRST = 1
and FSGM = 1, a frame-synchronization pulse is generated. The frame width value (FWID + 1) is counted
down on every CLKG cycle until it reaches 0, at which time FSG goes low. At the same time, the frame
period value (FPER + 1) is also counting down. When this value reaches 0, FSG goes high, indicating a
new frame.
15.8.17 Set the Receive Clock Mode
shows the settings for bits used to set receive clock mode.
Table 15-40. Register Bits Used to Set the Receive Clock Mode
Register
Bit
Name
Function
Type
Reset
Value
PCR
8
CLKRM
Receive clock mode
R/W
0
Case 1: Digital loopback mode not set (DLB = 0) in SPCR1.
CLKRM = 0
The MCLKR pin is an input pin that supplies the
internal receive clock (MCLKR).
CLKRM = 1
Internal MCLKR is driven by the sample rate
generator of the McBSP. The MCLKR pin is an
output pin that reflects internal MCLKR.
Case 2: Digital loopback mode set (DLB = 1) in SPCR1.
CLKRM = 0
The MCLKR pin is in the high impedance state.
The internal receive clock (MCLKR) is driven by
the internal transmit clock (CLKX). Internal
CLKX is derived according to the CLKXM bit of
PCR.
CLKRM = 1
Internal MCLKR is driven by internal CLKX. The
MCLKR pin is an output pin that reflects internal
MCLKR. Internal CLKX is derived according to
the CLKXM bit of PCR.
SPCR1
15
DLB
Digital loopback mode
R/W
00
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.