WM8255 datasheet(20/49 Pages) CIRRUS

20 / 49 page

Production Data

WM8255

PD, Rev 4.7, August 2013

Figure 13 State Mapping Functionality

STATERST = 11

STATE_0

SEQ_STATE = 00

STATE_1

SEQ_STATE = 01

STATE_2

SEQ_STATE = 10

STATE_3

SEQ_STATE = 11

STATE_0

SEQ_STATE = 00

STATE_1

SEQ_STATE = 01

STATERST = 01

Figure 14 Setting the Sequence Length with STATERST

LED CURRENT DRIVE SEQUENCE SYNCHRONISATION AND PROGRESSION

The trigger to progress the state machine through the sequence states is dependent on whether the

LED driver is operating in colour mode or monochrome mode.

COLOUR MODE

In Colour Mode operation, LEDSTART and TG are used to synchronise and progress the sequence

state machine. This allows a single LED change for each line scan.

With both LEDSTART and TG high, the sequence state machine is synchronously set to STATE_0 by

MCLK. With LEDSTART low and at the next high pulse of TG, the sequence state machine is

progressed to the next state, STATE_1, by MCLK. This is repeated until the maximum number of

states determined by STATERST has been reached. At this point the LED drive current will be

switched away from the selected LED. The sequence state machine will be held in this state until

restarted by LEDSTART and TG.

If at any time both TG and LEDSTART are high, the sequence is synchronously set back to STATE_0

by MCLK.

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