Reset and Initialization Procedure for the Sample Rate Generator
Sample Rate Generator of the McBSP
3-12
SPRU592E
3.5 Reset and Initialization Procedure for the Sample Rate Generator
To reset and initialize the sample rate generator:
1) Place the sample rate generator in reset.
During a DSP reset, the sample rate generator, the receiver, and the
transmitter reset bits (GRST, RRST, and XRST) are automatically forced
to 0. Otherwise, during normal operation, the sample rate generator can
be reset by making GRST = 0 in SPCR2, provided that CLKG and/or FSG
is not used by any portion of the McBSP. Depending on your system you
may also want to reset the receiver (RRST = 0 in SPCR1) and reset the
transmitter (XRST = 0 in SPCR2).
If GRST = 0 due to a DSP reset, CLKG is driven by the McBSP internal
input clock divided by 2, and FSG is driven inactive-low. If GRST = 0 due to
program code, CLKG and FSG are driven low (inactive).
2) Program registers that affect the sample rate generator.
Program the sample rate generator registers (SRGR1 and SRGR2) as
required for your application. If necessary, other control registers can be
loaded with desired values, provided the respective portion of the McBSP
(the receiver or transmitter) is in reset.
After the sample rate generator registers are programmed, wait 2
CLKSRG cycles. This ensures proper synchronization internally.
3) Enable the sample rate generator (take it out of reset).
In SPCR2, make GRST = 1 to enable the sample rate generator.
After the sample rate generator is enabled, wait 2 CLKG cycles for the
sample rate generator logic to stabilize.
On the next rising edge of CLKSRG, CLKG transitions to 1 and starts
clocking with a frequency equal to
CLKG frequency
+
Input clock frequency
(CLKGDV
)
1)
where the input clock is selected with the SCLKME bit of PCR and the
CLKSM bit of SRGR2:
SCLKME
CLKSM
Input Clock For
Sample Rate Generator
0
0
Signal on CLKS pin
0
1
McBSP internal input clock
1
0
Signal on CLKR pin
1
1
Signal on CLKX pin
Содержание TMS320VC5509
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