CLKG
FSG
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Frame-
CLKG
×
sync pulse width: (FWID + 1)
Frame-sync period: (FPER + 1)
CLKG
×
Preliminary
Architecture
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The values in FPER and FWID are loaded into separate down–counters. The 12–bit FPER counter
counts down the generated clock cycles from the programmed value (4095 maximum) to 0. The 8–bit
FWID counter counts down from the programmed value (255 maximum) to 0.
shows a frame–synchronization period of 16 CLKG periods (FPER = 15 or 0000 1111b)
and a frame–synchronization pulse with an active width of 2 CLKG periods (FWID = 1).
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.
Figure 11-32. Frame of 16 CLKG Periods and Active Width of 2 CLKG Periods
11.2.8.6.16 Set the Transmit Clock Mode
CLKXM bit (PCR_REG[9]) is used to set the transmit clock mode
shows how the CLKXM bit selects the transmit clock and the corresponding status of the
McBSP.CLKX pin. The CLKXP bit determines the polarity of the signal on the McBSP.CLKX pin.
If the sample rate generator creates a clock signal (CLKG) that is derived from an external input clock,
the GSYNC bit determines whether CLKG is kept synchronized with pulses on the McBSP.FSR pin.
In the digital loop-back mode (DLB = 1) or analog loop-back mode (ALB = 1), the transmit frame
synchronization signal is used as the receive frame synchronization signal.
Table 11-17. CLKXM Bit Effect on Transmit Clock and McBSP.CLKX Pin
CLKXM
Source of Transmit Clock
McBSP.CLKX Pin Status
0
Internal CLKX is driven by an external clock on the
Input
McBSP.CLKX pin. CLKX is inverted as determined by CLKXP
before being used.
1
Internal CLKX is driven by the sample rate generator clock,
Output. CLKG, inverted as determined by
CLKG.
CLKXP, is driven out on McBSP.CLKX.
1172
Multichannel Buffered Serial Port (McBSP)
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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