13

2088 1.1 04/11/05

SMS48

SUMMIT MICROELECTRONICS, Inc.

Preliminary Information

Figure 9 - Read and Write Operations

READ OPERATIONS

Read operations are initiated with the R/W bit of the

identification field set to 1. There are two different Read

options: 1. Current Address Byte Read, and 2. Random

Address Byte Read.

Random Address Read

Random address Read operations allow the Master to

access any register location in a random fashion. This

operation involves a two-step process. First, the Master

issues a write command which includes the start condition

and the Slave address field (with the R/W bit set to Write),

followed by the address of the word it is to Read. This

procedure sets the internal address counter of the SMS48

to the desired address. After the word address acknowl-

edge is received by the Master it immediately reissues a

Start condition, followed by another Slave address field

with the R/W bit set to READ. The SMS48 will respond with

an Acknowledge and then transmit the 8 data bits stored at

the addressed location. At this point the Master sets the

SDA line to NACK and generates a Stop condition. The

SMS48 discontinues data transmission and reverts to its

standby power mode.

N

A

C

K

A

C

K

R

/

W

A

C

K

D

7

D

6

D

5

D

4

D

3

D

2

D

1

D

0

A

C

K

S

T

O

P

S

T

A

R

T

Writing Configuration Registers

Master

SDA

Slave

01

10

Master

SDA

Slave

C

7

C

6

C

5

C

4

C

3

C

2

C

1

C

0

A

C

K

R

/

W

A

C

K

S

T

A

R

T

C

7

C

6

C

5

C

4

C

3

C

2

C

1

C

0

Reading the Configuration Register

01

10

A

C

K

R

/

W

S

T

O

P

S

T

A

R

T

D

7

D

6

D

5

D

4

D

3

D

2

D

1

D

0

01

10

B

A

2

B

A

1

X

B

A

2

B

A

1

X

B

A

2

B

A

1

X

Figure 10 - Write Flow Chart

Next

Operation

a Write?

ACK

Returned

Issue

Address

Proceed

With

Write

Await

Next

Command

Issue Stop

Issue Slave

Address and

R/W = 0

Issue Stop

Write Cycle

In Progress

Yes

No

Issue Start

Yes

No