Registers
1250
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Multichannel Buffered Serial Port (McBSP)
25.3.6 Sample Rate Generator Register (SRGR)
The sample rate generator register (SRGR) controls the operation of various features of the sample rate
generator. The SRGR is shown in
and described in
Figure 25-47. Sample Rate Generator Register (SRGR)
31
30
29
28
27
16
GSYNC
CLKSP
CLKSM
FSGM
FPER
R/W-0
R/W-0
R/W-1
R/W-0
R/W-0
15
8
7
0
FWID
CLKGDV
R/W-0
R/W-1
LEGEND: R/W = Read/Write; -n = value after reset
Table 25-28. Sample Rate Generator Register (SRGR) Field Descriptions
Bit
Field
Value
Description
31
GSYNC
Sample-rate generator clock synchronization bit is only used when the external clock (CLKS) drives
the sample-rate generator clock (CLKSM = 0).
0
The sample-rate generator clock (CLKG) is free running.
1
The sample-rate generator clock (CLKG) is running; however, CLKG is resynchronized and frame-
sync signal (FSG) is generated only after detecting the receive frame-synchronization signal (FSR).
Also, frame period (FPER) is a don't care because the period is dictated by the external frame-sync
pulse.
30
CLKSP
CLKS polarity clock edge select bit is only used when the external clock (CLKS) drives the sample-
rate generator clock (CLKSM = 0).
0
Rising edge of CLKS generates CLKG and FSG.
1
Falling edge of CLKS generates CLKG and FSG.
29
CLKSM
Sample rate generator input clock mode bit. The sample rate generator can accept an input clock
signal and divide it down according to CLKGDV to produce an output clock signal, CLKG. The
frequency of CLKG is:
CLKG frequency = Input clock frequency/( 1)
CLKSM is used in conjunction with the SCLKME bit in the pin control register (PCR) to determine
the source for the input clock.
A CPU reset selects the McBSP internal input clock as the input clock and forces the CLKG
frequency to 1/2 the McBSP internal input clock frequency.
0
The input clock for the sample rate generator is taken from the CLKS pin or from the CLKR pin,
depending on the value of the SCLKME bit in PCR:
CLKSM
SCLKME
Input Clock for Sample Rate Generator
0
0
Signal on CLKS pin
0
1
Signal on CLKR pin
1
The input clock for the sample rate generator is taken from the McBSP internal input clock or from
the CLKX pin, depending on the value of the SCLKME bit in PCR:
CLKSM
SCLKME
Input Clock for Sample Rate Generator
1
0
McBSP internal input clock
1
1
Signal on CLKX pin
28
FSGM
Sample-rate generator transmit frame-synchronization mode bit is only used when FSXM = 1 in
PCR.
0
Transmit frame-sync signal (FSX) is generated on every DXR-to-XSR copy. When FSGM = 0, FWID
bit and FPER bit are ignored.
1
Transmit frame-sync signal (FSX) is driven by the sample-rate generator frame-sync signal (FSG).
27-16
FPER
0-FFFh
Frame period value plus 1 specifies when the next frame-sync signal becomes active. Range is 1 to
4096 sample-rate generator clock (CLKG) periods.
15-8
FWID
0-FFh
Frame width value plus 1 specifies the width of the frame-sync pulse (FSG) during its active period.