ISD5216PI datasheet(20/75 Pages) WINBOND

20 / 75 page

ISD5216

- 20 -

7.4. I2S SERIAL INTERFACE

As shown in the following figure, the bus has three lines:

•

continuous serial clock (SCK)

•

word select (WS)

•

serial data (SDIO)and the device generating SCK and WS is the master.

Simple System Configurations and Basic Interface Timing

7.4.1. Serial Data

Serial data is transmitted in two’s complement with the MSB first. The MSB is transmitted first

because the transmitter and receiver may have different word lengths. It isn’t necessary for the

transmitter to know how many bits the receiver can handle, nor does the receiver need to know how

many bits are being transmitted.

When the system word length is greater than the transmitter word length, the word is truncated (least

significant data bits are set to ‘0’) for data transmission. If the receiver is sent more bits than its word

length, the bits after the LSB are ignored. On the other hand, if the receiver is sent fewer bits than its

word length, the missing bits are set to zero internally. And so, the MSB has a fixed position, whereas

the position of the LSB depends on the word length. The transmitter always sends the MSB of the

next word one clock period after the WS changes.

Serial data sent by the transmitter may be synchronized with either the trailing (HIGH-to-LOW) or the

leading (LOW-to-HIGH) edge of the clock signal. However, the serial data must be latched into the

receiver on the leading edge of the serial clock signal, and so there are some restrictions when

ISD5216PI 数据表(PDF) 20 Page - Winbond