XIO2221 datasheet(37/196 Pages) TI1

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b3 b2

b1 b0

b7 b6 b5 b4 b3 b2

b1 b0

Slave Address

Word Address

R/W

S/P =Start/StopCondition

A =Slave Acknowledgement

b7 b6

b3 b2

b1 b0

DataByte

b3 b2

b1 b0

b7 b6 b5 b4 b3 b2

b1 b0

Slave Address

Word Address

R/W

b3 b2

b1 b0

Slave Address

S/P =Start/StopCondition

M=Master Acknowledgement

b7 b6

b3 b2

b1 b0

DataByte

Start

Restart

R/W

A =Slave Acknowledgement

Stop

Slave Address

Word Address

R/W

DataByte1

DataByte2

DataByte3

M=Master Acknowledgement

S/P =Start/StopCondition

A =Slave Acknowledgement

DataByte0

Restart

R/W

Slave Address

Start

XIO2221

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SCPS216A – JULY 2009 – REVISED FEBRAURY 2010

Figure 3-9. Serial-Bus Protocol Byte Write

Figure 3-10 shows a single-byte read. The bridge issues a start condition and sends the 7-bit slave device

address, and the R/W command bit is equal to 0b (write). The slave device acknowledges if it recognizes

the slave address. Next, the EEPROM word address is sent by the bridge, and another slave

acknowledgment is expected. Then, the bridge issues a restart condition followed by the 7-bit slave

address, and the R/W command bit is equal to 1b (read). Once again, the slave device responds with an

acknowledge. Next, the slave device sends the 8-bit data byte, MSB first. Since this is a 1-byte read, the

bridge responds with no acknowledge (logic high) indicating the last data byte. Finally, the bridge issues a

stop condition.

Figure 3-10. Serial-Bus Protocol Byte Read

Figure 3-11 shows the serial interface protocol during a multibyte serial EEPROM download. The

serial-bus protocol starts exactly the same as a 1-byte read. The only difference is that multiple data bytes

are transferred. The number of transferred data bytes is controlled by the bridge master. After each data

byte, the bridge master issues acknowledge (logic low) if more data bytes are requested. The transfer

ends after a bridge master no acknowledge (logic high) followed by a stop condition.

Figure 3-11. Serial-Bus Protocol Multibyte Read

Feature/Protocol Descriptions

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