Sample Rate Generator
3-3
Sample Rate Generator of the McBSP
SPRU592E
The input clock for the sample rate generator (labeled CLKSRG in Figure 3
can be supplied by the McBSP internal input clock or by one of these external
pins: CLKX, CLKR, or (if present) CLKS. Not all C55x devices have a CLKS
pin; check the device-specific data manual. The input clock source is selected
with the SCLKME bit of PCR and the CLKSM bit of SRGR2. If a pin is used,
the polarity of the incoming signal can be inverted with the appropriate polarity
bit (CLKXP of PCR, CLKRP of PCR, or CLKSP of SRGR2).
Note:
On TMS320VC5501 and TMS320VC5502 devices, the polarity of the
sample rate generator input clock is always positive (rising edge), regardless
of CLKRP or CLKXP.
The sample rate generator has a 3-stage clock divider that gives CLKG and
FSG programmability. The three stages provide:
-
Clock divide down. The sample rate generator input clock is divided
according to the CLKGDV bits of SRGR1 to produce CLKG.
-
Frame period divide down. CLKG is divided according to the FPER bits of
SRGR2 to control the period from the start of a frame-sync pulse to the
start of the next pulse.
-
Frame-sync pulse width countdown. CLKG cycles are counted according
to the FWID bits of SRGR1 to control the width of each frame-sync pulse.
Note:
The maximum frequency for the McBSP on the TMS320VC5503/5507/5509
and TMS320VC5510 devices is 1/2 the CPU clock frequency. The maximum
frequency for the McBSP on the TMS320VC5501 and TMS320VC5502
devices is 1/2 the frequency of the slow peripherals clock. For more
information on programming the frequency of the slow peripheral clock, see
the
TMS320VC5501 Fixed-Point Digital Signal Processor Data Manual
(literature number SPRS206) or the
TMS320VC5502 Fixed-Point Digital
Signal Processor Data Manual
(literature number SPRS166). Other timing
limitations may also apply. See the device-specific data manual for detailed
information on the McBSP timing requirements.
When driving CLKX or CLKR at the pin, choose an appropriate input clock
frequency. When using the internal sample rate generator for CLKX and/or
CLKR, choose an appropriate input clock frequency and divide down value
(CLKGDV).
Содержание TMS320VC5509
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