DS4550 Datasheet, PDF(17/18 Page) Dallas Semiconductor – I2C and JTAG Nonvolatile 9-Bit I/O Expander Plus Memory

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

DS4550 Datasheet, PDF (17/18 Pages) Dallas Semiconductor – I2C and JTAG Nonvolatile 9-Bit I/O Expander Plus Memory

◁

I2C and JTAG Nonvolatile 9-Bit I/O

Expander Plus Memory

See Figure 6 for a read example using the repeated

start condition to specify the starting memory location.

Reading Multiple Bytes from a Slave: The read oper-

ation can be used to read multiple bytes with a single

transfer. When reading bytes from the slave, the master

simply ACKs the data byte if it desires to read another

byte before terminating the transaction. After the mas-

ter reads the last byte, it must NACK to indicate the end

of the transfer and generate a stop condition.

Applications Information

Power Supply Decoupling

To achieve best results, it is highly recommended that a

decoupling capacitor is used on the IC power-supply

pins. Typical values of decoupling capacitors are 0.01ÂµF

and 0.1ÂµF. Use a high-quality, ceramic, surface-mount

capacitor, and mount it as close as possible to the VCC

and GND pins of the IC to minimize lead inductance.

TYPICAL I2C WRITE TRANSACTION

MSB

LSB

MSB

LSB

MSB

LSB

START 1 0 1 0 A2 A1 A0 R/W SLAVE b7 b6 b5 b4 b3 b2 b1 b0 SLAVE b7 b6 b5 b4 b3 b2 b1 b0 SLAVE STOP

ACK

SLAVE

ADDRESS*

READ/

WRITE

DATA

*THE SLAVE ADDRESS IS DETERMINED BY ADDRESS PINS A0, A1, AND A2.

EXAMPLE I2C TRANSACTIONS (WHEN A0, A1, AND A2 ARE CONNECTED TO GND)

A) SINGLE BYTE WRITE

-WRITE I/O CONTROL 0

A0h

F2h

START 1 0 1 0 0 0 0 0 SLAVE 1 1 1 1 0 0 1 0 SLAVE 0 0 0 0 0 0 0 0 SLAVE

ACK

STOP

B) SINGLE BYTE READ

-READ I/O STATUS 0 RESISTER

A0h

F8h

START

1 0100000

SLAVE

ACK

11111 000

SLAVE

ACK

REPEATED

START

A1h

1 0 1 0 0 0 0 1 SLAVE

ACK

DATA

I/O STATUS

MASTER

NACK

STOP

C) SINGLE BYTE WRITE

-WRITE PULLUP ENABLE 0

A0h

F0h

FFh

START

1 0100000

SLAVE

ACK

11110 000

SLAVE

ACK

11111111

SLAVE

ACK

STOP

D) TWO BYTE WRITE

-WRITE I/O CONTROL 0 AND

I/O CONTROL 1 REGISTERS TO 00h

A0h

F2h

START

10100000

SLAVE

ACK

11110 010

SLAVE

ACK

00h

00000000

00h

SLAVE

ACK

00000000

SLAVE

ACK

STOP

D) TWO BYTE READ

-READ I/O STATUS 0 AND I/O

STATUS 1 RGISTERS

A0h

F8h

START 1 0 1 0 0 0 0 0

SLAVE

ACK

111 11000

SLAVE

ACK

A1h

DATA

REPEATED

START

1 0 1 0 0 0 0 1 SLAVE

ACK

I/O STATUS 0

MASTER

ACK

DATA

I/O STATUS 1

MASTER

NACK

STOP

Figure 6. I2C Communication Examples

____________________________________________________________________ 17

▷