Current data retransmitted
New data received
(R/X)SYNCERR
DX
DR
FS(R/X)
CLK(R/X)
C6C7B0
B2B3B4B5B7 B6B6B7A0 B1
D6D7C0C1C2C3C4C5C6C7B6B7A0
Frame synchronization aborts current transfer
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Transmitter Configuration
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SPRUI07–March 2020
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Multichannel Buffered Serial Port (McBSP)
12.9.11 Enable/Disable the Transmit Frame-Synchronization Ignore Function
Table 12-58. Register Bit Used to Enable/Disable the Transmit Frame-Synchronization Ignore
Function
Register Bit Name Function Type
Reset
Value
XCR2 2 XFIG Transmit frame-synchronization ignore R/W 0
XFIG = 0 An unexpected transmit frame-synchronization
pulse causes the McBSP to restart the frame
transfer.
XFIG = 1 The McBSP ignores unexpected transmit frame-
synchronization pulses.
12.9.11.1 Unexpected Frame-Synchronization Pulses and Frame-Synchronization Ignore
If a frame-synchronization pulse starts the transfer of a new frame before the current frame is fully
transmitted, this pulse is treated as an unexpected frame-synchronization pulse.
When XFIG = 1, normal transmission continues with unexpected frame-synchronization signals ignored.
When XFIG = 0 and an unexpected frame-synchronization pulse occurs, the serial port:
1. Aborts the present transmission
2. Sets XSYNCERR to 1 in SPCR2
3. Reinitiates transmission of the current word that was aborted
For more details about the frame-synchronization error condition, see Section 12.5.6.
12.9.11.2 Examples Showing the Effects of XFIG
Figure 12-51 shows an example in which word B is interrupted by an unexpected frame-synchronization
pulse when (R/X)FIG = 0. In the case of transmission, the transmission of B is aborted (B is lost). This
condition is a transmit synchronization error, which sets the XSYNCERR bit. No new data has been
written to DXR[1,2]; therefore, the McBSP transmits B again.
Figure 12-51. Unexpected Frame-Synchronization Pulse With (R/X) FIG = 0
In contrast with Figure 12-51, Figure 12-52 shows McBSP operation when unexpected frame-
synchronization signals are ignored (when (R/X)FIG = 1). Here, the transfer of word B is not affected by
an unexpected frame-synchronization pulse.
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