Setting the Receive Clock Polarity
Receiver Configuration
7-34
SPRU592E
7.20 Setting the Receive Clock Polarity
clock polarity.
Figure 7
−
22. Register Bit Used to Set Receive Clock Polarity
PCR
15
1
0
CLKRP
R/W-0
Legend:
R = Read; W = Write; -
n
= Value after reset
Table 7
−
25. Register Bit Used to Set Receive Clock Polarity
Register
Bit
Name
Function
PCR
0
CLKRP
Receive Clock Polarity
CLKRP = 0
When CLKR is configured as a input, the external CLKR is
not inverted before being used internally.
When CLKR is configured as an output, the internal CLKR
is not inverted before being driven on the CLKR pin.
The receive data is sampled on the falling edge of the
external CLKR signal.
CLKRP = 1
When CLKR is configured as a input, the external CLKR is
inverted before being used internally.
When CLKR is configured as an output, the internal CLKR
is inverted before being driven on the CLKR pin.
The receive data is sampled on the rising edge of the
external CLKR signal.
7.20.1 About Frame Sync Pulses, Clock Signals, and Their Polarities
Receive frame-sync pulses can be either generated internally by the sample
rate generator or driven by an external source. The source of frame sync is
selected by programming the mode bit, FSRM, in PCR. FSR is also affected
by the GSYNC bit in SRGR2. Similarly, receive clocks can be selected to be
inputs or outputs by programming the mode bit, CLKRM, in the PCR.
When FSR and FSX are inputs (FSXM = FSRM= 0, external frame-sync
pulses), the McBSP detects them on the internal falling edge of clock, internal
CLKR, and internal CLKX, respectively. The receive data arriving at the DR pin
is also sampled on the falling edge of internal CLKR. Note that these internal
clock signals are either derived from external source via CLK(R/X) pins or
driven by the sample rate generator clock (CLKG) internal to the McBSP.
Содержание TMS320VC5509
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