McBSP Transmission
2-17
McBSP Operation
SPRU592E
2.6 McBSP Transmission
This section explains the fundamental process of transmission in the McBSP.
For details about how to program the McBSP transmitter, see Chapter 8,
Transmitter Configuration
.
14 show how transmission occurs in the McBSP.
13 shows the physical path for the data. Figure 2
diagram showing signal activity for one possible transmission scenario. A
description of the process follows the figures.
Figure 2
−
13. McBSP Transmission Physical Data Path
ÁÁÁÁ
ÁÁÁÁ
DX
XSR[1,2]
ÁÁÁ
ÁÁÁ
DXR[1,2]
From CPU or
DMA controller
Compress
Do not modify
or
XSR[1,2]: Transmit shift registers 1 and 2
DXR[1,2]: Data transmit registers 1 and 2
Figure 2
−
14. McBSP Transmission Signal Activity
Write to DXR1
DXR1 to XSR1 copy(C)
Write to DXR1(C)
DXR1 to XSR1 copy(B)
XRDY
DX
FSX
CLKX
C5
C6
C7
B0
B1
B2
B3
B4
B5
B6
B7
A0
A1
Á
Á
ÁÁ
ÁÁ
Á
Á
Á
Á
CLKX: Internal transmit clock
FSX: Internal transmit frame-sync signal
DX: Data on DX pin
XRDY: Status of transmitter ready bit (high is 1)
1) The CPU or the DMA controller writes data to the data transmit register(s).
When DXR1 is loaded, the transmitter ready bit (XRDY) is cleared in
SPCR2 to indicate that the transmitter is not ready for new data.
If the word length is 16 bits or smaller, only DXR1 is used. If the word length
is larger than 16 bits, DXR2 and DXR1 are used, and DXR2 contains the
most significant bits.
Note:
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.
Содержание TMS320VC5509
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