
TXCLKESC
TURNREQUEST
DP/DN
DIRECTION
LP-11
LP-10
LP-00
LP-10
LP-00
LP-00
LP-00
LP-00
LP-00
LP-10
LP-11
LP state driven by remote LPTX
LP state driven by DSI PHY LPTX
dss-401
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Display Subsystem Basic Programming Model
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The PHY then goes through the LP End of Transmission (EoT) procedure. THS-TRAIL and THS-EXIT are
also multiples of CLKIN4DDR and programmed by the following register bit fields:
•
THS-TRAIL timing is programmed by the DSS.
[15:8] REG_THSTRAIL bit field.
•
THS-EXIT timing is programmed by the DSS.
[7:0] REG_THSEXIT bit field.
The PHY completes the SoT and EoT procedures, once begun, irrespective of any change in PPI signals.
If TXREQUESTHS goes low during the SoT procedure, the PHY start the EoT procedure immediately
after finishing the SoT procedure and no data is transmitted.
STOPSTATE is high whenever the line is in LP-11 state, as determined by the outputs of the low power
receivers. This signal is not synchronized with TXByteClkHS.
The protocol must ensure that TXREQUESTESC, TXULPSCLK, and TURNREQUEST are low whenever
TXREQUESTHS is asserted.
7.5.6.4.3 Turn-Around Request in Transmit Mode
When the DSI PHY is in transmit mode, the DSI protocol engine can request a turnaround by making the
TurnRequest signal high for at least one clock cycle of TxClkEsc (see
, TurnRequest
FSM).
The DSI PHY transmits the turn-around request pattern (LP 11-10-00-10-00-00-00-00) (see
).
The number of 00 states in the end of the pattern is defined by T
TA-GO
timing parameter and is
programmable through the DSS.
[31:29] REG_TTAGO bit field, in number of
TxClkEsc clocks. Following the transmission of the pattern, the DSI PHY disables its LP transmitters and
waits for an acknowledgment from the remote device. The remote device detects the turn-around request
and acknowledges it by driving LP-10, followed by the STOP state. When this acknowledgment is
received, DSI PHY switches to receive mode and indicates the completion of the turn-around procedure
by changing the direction (BTA_IRQ is asserted, as described in
, Bus Turnaround).
Figure 7-142. Turn-Around Request in Transmit Mode
The DSI protocol engine must not stop TxClkEsc after the turn-around process completes (the
DSS.
[20] LP_CLK_ENABLE bit must be kept at 1), because TxClkEsc is also used in
handling a turn-around request transmitted by a remote slave device (see
, Turn-Around
Request in Receive Mode).
7.5.6.4.4 Turn-Around Request in Receive Mode
When the DSI PHY is in receive mode, an LP pattern of 11-10-00-10-00 on DP/DN lines indicates a
turn-around request from the remote device (see
).
1762
Display Subsystem
SWPU177N – December 2009 – Revised November 2010
Copyright © 2009–2010, Texas Instruments Incorporated