Receive Data Clocking - Texas Instruments TMS320C6201 Reference Manual

Figure 11–7.Receive Data Clocking
CLKR_int
DR
11.3.4.2 Frame Synchronization Phases
In a system where the same clock (internal or external) is used to clock the re-
ceiver and transmitter, CLKRP = CLKXP. The receiver uses the opposite edge
as the transmitter to ensure valid setup and hold times of data around this edge.
Figure 11–7 shows how data clocked by an external serial device using a rising-
edge clock can be sampled by the McBSP receiver with the falling edge of the
same clock.
Frame synchronization indicates the beginning of a transfer on the McBSP.
The data stream following frame synchronization can have up to two phases,
phase 1 and phase 2. The number of phases can be selected by the phase bit,
(R/X)PHASE, in the RCR and XCR. The number of elements per frame and
bits per element can be independently selected for each phase via
(R/X)FRLEN(1/2) and (R/X)WDLEN(1/2), respectively. Figure 11–8 shows a
frame in which the first phase consists of two elements of 12 bits each followed
by a second phase of three elements of 8 bits each. The entire bit stream in
the frame is contiguous; no gaps exist either between elements or phases.
Table 11–9 shows the fields in the receive/transmit control registers (RCR/
XCR) that control the frame length and element length for each phase for both
the receiver and the transmitter. The maximum number of elements per frame
is 128 for a single-phase frame and 256 elements in a dual-phase frame. The
number of bits per element can be 8, 12, 16, 20, 24, or 32.
Note:
For a dual-phase frame with internally generated frame sync, the maximum
number of elements per phase depends on the word length. This is because
the frame period, FPER is only 12-bits wide and, therefore, provides 4 096
bits per frame. Hence, the maximum number of 128 elements per single-
phase frame for a total of 256 elements per dual-phase frame applies only
when the WDLEN is 16-bits.
Data setup
B7
Multichannel Buffered Serial Ports
Data Transmission and Reception
Data hold
B6
11-25