Current data retransmitted
New data received
(R/X)SYNCERR
DX
DR
FS(R/X)
CLK(R/X)
C6
C7
B0
ÁÁ
ÁÁ
ÁÁ
B2
B3
B4
B5
B7
B6
B6
B7
A0
B1
D6
D7
C0
C1
C2
C3
C4
C5
C6
C7
B6
B7
A0
ÁÁ
ÁÁ
ÁÁ
ÁÁ
Frame synchronization aborts current transfer
Transmitter Configuration
1104
SPRUH22I – April 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Multichannel Buffered Serial Port (McBSP)
15.9.10 Enable/Disable the Transmit Frame-Synchronization Ignore Function
Table 15-57. 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.
15.9.10.1 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
Unexpected
Transmit Frame-Synchronization Pulse
.
15.9.10.2 Examples Showing the Effects of XFIG
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 15-51. Unexpected Frame-Synchronization Pulse With (R/X) FIG = 0
In contrast with
,
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.