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Display Subsystem Basic Programming Model
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When the DSS.
[0] IF_EN bit is reset by software, the hardware should finish the transfer of the
pending data in the TX FIFO and wait for response if BTA has been sent (Protocol engine is receive
mode), then the hardware resets the DSS.
[0] IF_EN bit. When using the video mode, the VC
associated with the video port should be enabled prior to enable the interface according to the following
sequence:
•
DSS.
[0] IF_EN bit is equal to 0
•
Enable the VC associated with video mode by setting the DSS.
[0] VC_EN
•
Set the DSS.
[0] IF_EN bit to 1
7.5.4.5
Virtual Channels
There is one set of registers for each VC. The attributes of the VC define the following characteristics:
•
Transfer mode (DSS.
[4] MODE bit):
–
Video mode
–
Command mode
•
Data type
•
Source (DSS.
[1] SOURCE bit)
–
Video port
–
L4 interconnect port
•
HS or LP forward transmission
•
Automatic bus turn-around generation
–
Short packets (DSS.
[2] BTA_SHORT_EN bit)
–
Long packets (DSS.
[3] BTA_LONG_EN bit)
•
DMA request configurations for RX and TX
–
DMA request number (DSS.
[29:27] DMA_RX_REQ_NB bit field for RX FIFO and
[23:21] DMA_TX_REQ_NB bit field for TX FIFO)
–
DMA threshold (DSS.
[26:24] DMA_RX_THRESHOLD bit field for RX FIFO and
[19:17] DMA_TX_THRESHOLD bit field for TX FIFO)
•
Mode speed (DSS.
[9] MODE_SPEED bit)
•
ECC transmission (DSS.
[8] ECC_TX_EN bit)
•
CS transmission (DSS.
[7] CS_TX_EN bit)
The VC ID not calculated by the DSI module but provided while writing into the registers
and
.
7.5.4.6
Packets
The DSS.
register is used to send only short packets (ECC can be
calculated by hardware or by software user for debug purpose). The register is not used for video mode
data since the short packets are generated by the hardware using the following information:
•
synchronization events received on the video port (assertion/deassertion of the HSYNC and VSYNC
input signals)
•
DSS.
[18] VP_HSYNC_END
•
DSS.
[17] VP_HSYNC_START
•
DSS.
[16] VP_VSYNC_END
•
DSS.
[15] VP_VSYNC_START
•
DSS.
[10] VP_HSYNC_POL
•
DSS.
[11] VP_VSYNC_POL
•
DSS.
[1] SOURCE
The DSS.
register is used to provide header for long packets (ECC
is always calculated by hardware). The register is used for video mode and command mode. If the video
mode is enabled for the VC, it is not possible to transfer concurrently (interleaved in a frame) data using
1740
Display Subsystem
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated