Public Version
www.ti.com
McBSP Basic Programming Model
The DXENA bit controls the delay enabler on the mcbsp_dx pin. Set DXENA to enable an extra delay for
turn–on time. This bit does not control the data itself, so only the first bit is delayed (the delay is given by a
combinatorial delay buffer). The inserted delay: 18 ns, 26 ns (default), 35 ns, or 42 ns can be set using the
McBSPi.
[13:12] DXENDLY field. If you tie together the mcbsp_dx pins of multiple
McBSP modules, make sure DXENA=1, to avoid having more than one McBSP transmitting on the data
line at one time.
21.5.1.6.2.2.7 Set the Transmit Interrupt Mode
See
21.5.1.6.2.2.8 Set the Transmit DMA Mode
The McBSP transmit data DMA requests (McBSPi_DMA_TX) are active after the transmit
McBSPi.
[0] XRST bit is released. After reset, the default DMA threshold (and
length) is 1.
The transmit DMA requests can be disabled by setting the McBSPi.
[3] XDMAEN
bit to 0. When disabling the DMA, the DMA request line is deasserted even if a DMA transfer is pending,
and the DMA state-machine is not reset.
To configure the McBSP transmit data DMA requests, follow this procedure:
•
Write the transmit McBSPi.
register with the required transmit DMA request
length (the length of the transfer is the same as the threshold value + 1).
•
As long as the free locations level in XB is above or equal to the THRSH2_REG value + 1, the DMA
request is asserted.
•
After transferring the configured (THRSH2_REG value + 1) number of words, the transmit DMA
request is deasserted, and then reasserted as soon as the conditions are met again.
21.5.1.6.2.3 Frame-Synchronization Behavior
21.5.1.6.2.3.1 Set the Transmit Frame-Sync Mode
McBSPi.
[11] FSXM bit and McBSPi.
[12] FSGM bit are
used to set the transmit frame-sync mode.
shows how FSXM and FSGM select the source of transmit frame-synchronization pulses. The
three choices are:
1. External frame-synchronization input
2. Sample rate generator frame-synchronization signal (FSG)
3. Sample rate generator frame-synchronization signal (FSG) gated by the transmit buffer XB empty
condition.
also shows the effect of each bit setting on the mcbsp_fsx pin. The FSXP bit determines the
polarity of the signal on the mcbsp_fsx pin.
Table 21-32. How FSXM and FSGM Select the Source of Transmit Frame-Sync Pulses
FSXM
FSGM
Source of Transmit Frame Synchronization
mcbsp_fsx Pin Status
0
0 or 1
An external FSG enters the McBSP through the
Input
mcbsp_fsx pin. The signal is then inverted by FSXP
bit before being used as internal FSX.
1
1
Internal FSX is driven by the SRG FSG.
Output. FSG is inverted by FSXP bit before
being driven out on mcbsp_fsx pin.
1
0
A XB empty condition causes the McBSP not to
Output. The generated frame-synchronization
generate a transmit frame-synchronization pulse.
pulse is inverted as determined by FSXP bit
The frame synchronization is generated taking into
before being driven out on mcbsp_fsx pin.
account the FWID and FPER bits as long as the
transmit buffer is not empty. When the buffer is
empty the generated frame synchronization signal is
gated.
3147
SWPU177N – December 2009 – Revised November 2010
Multi-Channel Buffered Serial Port
Copyright © 2009–2010, Texas Instruments Incorporated
Содержание OMAP36 Series
Страница 174: ...174 List of Tables SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 692: ...692 MPU Subsystem SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 1084: ...1084 IVA2 2 Subsystem SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 1990: ...1990 2D 3D Graphics Accelerator SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 2334: ...2334 Memory Subsystem SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 2700: ...2700 Memory Management Units SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 2868: ...2868 HDQ 1 Wire SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 2974: ...2974 UART IrDA CIR SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3054: ...3054 Multichannel SPI SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3462: ...3462 MMC SD SDIO Card Interface SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3508: ...3508 General Purpose Interface SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3584: ...3584 Initialization SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...
Страница 3648: ...3648 Debug and Emulation SWPU177N December 2009 Revised November 2010 Copyright 2009 2010 Texas Instruments Incorporated ...