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A2
D(R/X)
FS(R/X)
C14
C15
B0
B2
B3
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B14
B15
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A1
B1
CLK(R/X)
Maximum frame frequency
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clock frequency
Number of bits per frame
Frame frequency
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Bit
*
clock frequency
Number of bit clocks between frame sync signals
Architecture
1212
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Multichannel Buffered Serial Port (McBSP)
25.2.7.3 Maximum Frame Frequency
The frame frequency is determined by the following equation, which calculates the period between frame
synchronization signals:
The frame frequency may be increased by decreasing the time between frame synchronization signals in
bit clocks (which is limited only by the number of bits per frame). As the frame transmit frequency is
increased, the inactivity period between the data frames for adjacent transfers decreases to 0. The
minimum time between frame synchronization pulses is the number of bits transferred per frame. This
time also defines the maximum frame frequency, which is calculated by the following equation:
shows the McBSP operating at maximum frame frequency. The data bits in consecutive
frames are transmitted continuously with no inactivity between bits. If there is a 1-bit data delay, as shown,
the frame synchronization pulse overlaps the last bit transmitted in the previous frame.
Figure 25-18. Maximum Frame Frequency for Transmit and Receive
NOTE:
For (R/X)DATDLY = 0, the first bit of data transmitted is asynchronous to CLKX, as shown in
.
Maximum frame frequency may not be possible when the word length is 8-bits, depending on
the clock divide value CLKGDV. The CPU or EDMA may not be able to service serial port
requests that occur as frequently as every 8-bit clocks. This situation can be resolved by
allowing additional space between words or choosing a slower bit clock (larger CLKGDV
value).