McBSP Transmission
McBSP Operation
2-18
SPRU592E
2) When new data arrives in DXR1, the McBSP copies the content of the data
transmit register(s) to the transmit shift register(s). In addition, the transmit
ready bit (XRDY) is set. This indicates that the transmitter is ready to
accept new data from the CPU or the DMA controller.
If the word length is 16 bits or smaller, only XSR1 is used. If the word length
is larger than 16 bits, XSR2 and XSR1 are used, and XSR2 contains the
most significant bits.
If companding is used during the transfer (XCOMPAND = 10b or 11b in
XCR2), the McBSP compresses the 16-bit data in DXR1 to 8-bit data in the
µ
-law or A-law format in XSR1. If companding is disabled, the McBSP
passes data from the DXR(s) to the XSR(s) without modification.
3) The McBSP waits for a transmit frame-sync pulse on internal FSX.
4) When the pulse arrives, the McBSP inserts the appropriate data delay that
is selected with the XDATDLY bits of XCR2.
In the preceding timing diagram (Figure 2
selected.
5) The McBSP shifts data bits from the transmit shift register(s) to the DX pin.
When activity is not properly timed, errors can occur. See the following topics
in Chapter 4 for more details:
-
Overwrite in the Transmitter
-
Underflow in the Transmitter
-
Unexpected Transmit Frame-Sync Pulse
Содержание TMS320VC5509
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