Data Packing Using Word Length and the Frame-Sync Ignore Function
Data Packing Examples
11-4
SPRU592E
11.2 Data Packing Using Word Length and the Frame-Sync 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-sync pulses. First, consider Figure 11
3, which shows the
McBSP operating at the maximum packet frequency. Here, each frame only
has a single 8-bit word. Note the frame-sync 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 11
−
3.8-Bit Data Words Transferred at Maximum Packet Frequency
RBR1 to
DRR1 copy
DRR1 copy
RBR1 to
RBR1 to
DRR1 copy
DRR1 copy
RBR1 to
DXR1 to XSR1
copy
DXR1 to XSR1
copy
DXR1 to XSR1
copy
DXR1 to XSR1
copy
Word 1
Word 2
Word 3
Word 4
CLKR
FSR
DR
CLKX
FSX
DX
4 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-sync 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.
Summary of Contents for TMS320VC5509
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