Frame ignored Frame ignored
FSX
DX
Frame ignored
DXR1 to XSR1 copy
DR
FSR
CLKR
RBR1 to DRR1 copy
RBR2 to DRR2 copy
Frame ignoredFrame ignoredFrame ignored
DX
FSX
CLKX
DR
FSR
CLKR
DXR1 to XSR1 copyDXR1 to XSR1 copyDXR1 to XSR1 copyDXR1 to XSR1 copy
RBR1 to DRR1 copyRBR1 to DRR1 copyRBR1 to DRR1 copyRBR1 to DRR1 copy
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Data Packing Examples
741
SPRUI07–March 2020
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Multichannel Buffered Serial Port (McBSP)
12.11.2 Data Packing Using Word Length and the Frame-Synchronization Ignore Function
When there are multiple words per frame, you can implement data packing by increasing the word length
(defining a serial word with more bits) and by ignoring frame-synchronization pulses. First, consider
Figure 12-63, which shows the McBSP operating at the maximum packet frequency. Here, each frame
only has a single 8-bit word. Notice the frame-synchronization pulse that initiates each frame transfer for
reception and for transmission. For reception, this configuration requires one read operation for each
word. For transmission, this configuration requires one write operation for each word.
Figure 12-63. 8-Bit Data Words Transferred at Maximum Packet Frequency
Figure 12-64 shows the McBSP configured to treat this data stream as a continuous 32-bit word. In this
example, the McBSP responds to an initial frame-synchronization pulse. However, (R/X)FIG = 1 so that
the McBSP ignores subsequent pulses. Only two read transfers or two write transfers are needed every
32 bits. This configuration effectively reduces the required bus bandwidth to half the bandwidth needed to
transfer four 8-bit words.
Figure 12-64. Configuring the Data Stream of Figure 12-63 as a Continuous 32-Bit Word
12.12 Interrupt Generation
McBSP registers can be programmed to receive and transmit data through DRR2/DRR1 and DXR2/DXR1
registers, respectively. The CPU can directly access these registers to move data from memory to these
registers. Interrupt signals will be based on these register pair contents and its related flags.
MRINT/MXINT will generate CPU interrupts for receive and transmit conditions.
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