I5216 Datasheet, PDF (75/83 Pages) Winbond – 8 TO 16 MINUTE VOICE RECORD/PLAYBACK SYSTEM WITH INTEGRATED CODEC

I5216 SERIES
Advanced Information
PRELIMINARY
WORD SELECT
The word select line indicates the channel being transmitted:
• WS = 0; channel 1 (left)
• WS = 1; channel 2 (right)
WS may change either on a trailing or leading edge of the serial clock, but it doesn’t need to be
symmetrical. In the slave, this signal is latched on the leading edge of the clock signal. The WS line
changes one clock period before the MSB is transmitted. This allows the slave transmitter to derive
synchronous timing of the serial data that will be set up for transmission. Furthermore, it enables the
receiver to store the previous word and clear the input for the next word (see figure Timing for I²S
Transmitter on previous page.)
TIMING
In the I²S format, any device can act as the system master by providing the necessary clock signals. A
slave will usually derive its internal clock signal from an external clock input. This means, taking into
account the propagation delays between master clock and the data and/or word-select signals, that the
total delay is simply the sum of:
• the delay between the external (master) clock and the slave’s
internal clock; and
• the delay between the internal clock and the data and/or
word-select signals.
For data and word-select inputs, the external to internal clock delay is of no consequence because it
only lengthens the effective set-up time (see figure Timing for I²S Transmitter on previous page.) The
major part of the time margin is to accommodate the difference between the propagation delay of the
transmitter, and the time required to set up the receiver.
All timing requirements are specified relative to the clock period or to the minimum allowed clock
period of a device. This means that higher data rates can be used in the future.
Timing for I²S Receiver
T = clock period
TR = minimum allowed clock period for transmitter
T > TR
Note that the specifications are defined by the transmitter speed. The specification of the receiver has to be able
to match the performance of the transmitter.
Publication Release Date: November 30, 2001
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Revision A1