McBSP Registers
1162
SPRUHE8E – October 2012 – Revised November 2019
Copyright © 2012–2019, Texas Instruments Incorporated
C28 Multichannel Buffered Serial Port (McBSP)
Table 15-73. Serial Port Control 2 Register (SPCR2) Field Descriptions (continued)
Bit
Field
Value
Description
5-4
XINTM
0-3h
Transmit interrupt mode bits. XINTM determines which event in the McBSP transmitter generates a
transmit interrupt (XINT) request. If XINT is properly enabled, the CPU services the interrupt request;
otherwise, the CPU ignores the request.
0
The McBSP sends a transmit interrupt (XINT) request to the CPU when the XRDY bit changes from 0
to 1, indicating that transmitter is ready to accept new data (the content of DXR[1,2] has been copied
to XSR[1,2]).
Regardless of the value of XINTM, you can check XRDY to determine whether a word transfer is
complete.
The McBSP sends an XINT request to the CPU when 16 enabled bits have been transmitted on the
DX pin.
1h
In the multichannel selection mode, the McBSP sends an XINT request to the CPU after every 16-
channel block is transmitted in a frame.
Outside of the multichannel selection mode, no interrupt request is sent.
2h
The McBSP sends an XINT request to the CPU when each transmit frame-synchronization pulse is
detected. The interrupt request is sent even if the transmitter is in its reset state.
3h
The McBSP sends an XINT request to the CPU when the XSYNCERR bit is set, indicating a transmit
frame-synchronization error.
Regardless of the value of XINTM, you can check XSYNCERR to determine whether a transmit frame-
synchronization error occurred.
3
XSYNCERR
Transmit frame-synchronization error bit. XSYNCERR is set when a transmit frame-synchronization
error is detected by the McBSP. If XINTM = 11b, the McBSP sends a transmit interrupt (XINT) request
to the CPU when XSYNCERR is set. The flag remains set until you write a 0 to it or reset the
transmitter.
If XINTM = 11b, writing a 1 to XSYNCERR triggers a transmit interrupt just as if a transmit frame-
synchronization error occurred.
For details about this error see
Unexpected Transmit Frame-Synchronization Pulse
.
0
No error
1
Transmit frame-synchronization error
2
XEMPTY
Transmitter empty bit. XEMPTY is cleared when the transmitter is ready to send new data but no new
data is available (transmitter-empty condition). This bit has a negative polarity; a transmitter-empty
condition is indicated by XEMPTY = 0.
0
Transmitter-empty condition
Typically this indicates that all the bits of the current word have been transmitted but there is no new
data in DXR1. XEMPTY is also cleared if the transmitter is reset and then restarted.
For more details about this error condition, see
,
Underflow in the Transmitter
.
1
No transmitter-empty condition
1
XRDY
Transmitter ready bit. XRDY is set when the transmitter is ready to accept new data in DXR[1,2].
Specifically, XRDY is set in response to a copy from DXR1 to XSR1.
If the transmit interrupt mode is XINTM = 00b, the McBSP sends a transmit interrupt (XINT) request to
the CPU when XRDY changes from 0 to 1.
Also, when XRDY changes from 0 to 1, the McBSP sends a transmit synchronization event (XEVT)
signal to the DMA controller.
0
Transmitter not ready
When DXR1 is loaded, XRDY is automatically cleared.
1
Transmitter ready: DXR[1,2] is ready to accept new data.
If both DXRs are needed (word length larger than 16 bits), the CPU or the DMA controller must load
DXR2 first and then load DXR1. As soon as DXR1 is loaded, the contents of both DXRs are copied to
the transmit shift registers (XSRs), as described in the next step. If DXR2 is not loaded first, the
previous content of DXR2 is passed to the XSR2.