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Display Subsystem Functional Description
before TxByteClkHS is stopped. This latency must be accounted for to prevent any issue when
DSIStopClk is deasserted soon after being asserted. This is done using a hardware timer programmed
using the DSS.
[7:0] DSI_STOPCLK_LATENCY bit field. This timer is
programmed in number of periods of the DSI Protocol functional clock (DSI_FCLK). At reset value, the
timer is programmed with 0x80 (128) value.
CAUTION
The
programmed
value
in
the
DSS.
DSI_STOPCLK_LATENCY bit field must be greater than ((3 x L3_ICLK period)
+ (5 x CLKIN4DDR period))/(DSI_FCLK period).
7.4.3.7
Timers
NOTE:
Among the timers described in this section, only the HS TX, LP RX and turnRequests timers
generates interrupts immediately when the timer value is null. For ForceTxStopMode timer, it
ends counting instantly and ForceTxStopMode is not asserted.
7.4.3.7.1 Twakeup Timer
The T
WakeUp
timer is not implemented in the DSI protocol engine. The software must use a general-purpose
(GP) timer to handle this. This timer is used for existing ULP status mode for the active lanes (clock and/or
data lanes). The sequence to exit ULP state is:
1. Change the state of TxULPSExit for each lane to ACTIVE.
2. Wait for the interrupt indicating that all lanes with TxULPSExit active have acknowledged by asserting
ULPSActiveNot. This is done by reading the DSS.
ULPSACTIVENOT_ALLi_IRQ bit fields (i = 0, 1).
3. Start the application wake-up timer (GP timer).
4. Wait for the time-out.
5. Change the TxUlpsClk signals to INACTIVE state for the clock lane and/or TxRequestEsc INACTIVE
state for the data lane(s).
NOTE:
The minimum time for the wake-up period is 1 ms.
To enter ULPS mode for clock lane, TxUlpsClk state must be changed to active state. To enter ULPS
mode for data lane, TxRequestEsc state must be changed to active state (TxUlpsEsc as well if it is not
already in active state).
7.4.3.7.2 ForceTxStopMode FSM
The signal ForceTxStopMode is used at initialization time (DSI complex I/O).
describes the
ForceTxStopMode FSM to assert/deassert ForceTxStopMode signal.
1675
SWPU177N – December 2009 – Revised November 2010
Display Subsystem
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