15.2.3.6 Frame Frequency
The frame frequency is determined by the period between frame-synchronization pulses and is defined as
shown by
Frame Frequency
+
Clock Frequency
Number of Clock Cycles Between Frame- Sync Pulses
(10)
The frame frequency can be increased by decreasing the time between frame-synchronization pulses (limited
only by the number of bits per frame). As the frame transmit frequency increases, the inactivity period between
the data packets for adjacent transfers decreases to zero.
15.2.3.7 Maximum Frame Frequency
The minimum number of clock cycles between frame synchronization pulses is equal to the number of bits
transferred per frame. The maximum frame frequency is defined as shown by
Maximum Frame Frequency
+
Clock Frequency
Number of Bits Per Frame
(11)
shows the McBSP operating at maximum packet frequency. At maximum packet frequency, the data
bits in consecutive packets are transmitted contiguously with no inactivity between bits.
D(R/X)
FS(R/X)
CLK(R/X)
C6
C7
B0
B1
B2
B3
B4
B5
B6
B7
A0
A1
A2
Figure 15-8. McBSP Operating at Maximum Packet Frequency
If there is a 1-bit data delay as shown in this figure, the frame-synchronization pulse overlaps the last
bit transmitted in the previous frame. Effectively, this permits a continuous stream of data, making frame-
synchronization pulses redundant. Theoretically, only an initial frame-synchronization pulse is required to initiate
a multipacket transfer.
The McBSP supports operation of the serial port in this fashion by ignoring the successive frame-synchronization
pulses. Data is clocked into the receiver or clocked out of the transmitter during every clock cycle.
Note
For XDATDLY = 0 (0-bit data delay), the first bit of data is transmitted asynchronously to the internal
transmit clock signal (CLKX). For more details, see
15.2.4 Frame Phases
The McBSP allows you to configure each frame to contain one or two phases. The number of words and the
number of bits per word can be specified differently for each of the two phases of a frame, allowing greater
flexibility in structuring data transfers. For example, you might define a frame as consisting of one phase
containing two words of 16 bits each, followed by a second phase consisting of 10 words of 8 bits each. This
configuration permits you to compose frames for custom applications or, in general, to maximize the efficiency of
data transfers.
15.2.4.1 Number of Phases, Words, and Bits Per Frame
shows which bit-fields in the receive control registers (RCR1 and RCR2) and in the transmit control
registers (XCR1 and XCR2) determine the number of phases per frame, the number of words per frame, and
number of bits per word for each phase, for the receiver and transmitter. The maximum number of words per
Multichannel Buffered Serial Port (McBSP)
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
TMS320x2806x Microcontrollers
885
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Содержание TMS320 2806 Series
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