ADM1067ASU datasheet(30/32 Pages) AD

30 / 32 page

ADM1067

Rev. B | Page 30 of 32

•

To set up a 2-byte EEPROM address for a subsequent read,

write, block read, block write, or page erase. In this case,

the command byte is the high byte of the EEPROM address

from 0xF8 to 0xFB. The only data byte is the low byte of

the EEPROM address, as shown in Figure 36.

SLAVE

ADDRESS

EEPROM

ADDRESS

HIGH BYTE

(0xF8 TO 0xFB)

SW A

EEPROM

ADDRESS

LOW BYTE

(0x00 TO 0xFF)

Figure 36. Setting an EEPROM Address

Because a page consists of 32 bytes, only the 3 MSBs of the

address low byte are important f or page erasure. The lower

five bits of the EEPROM address low byte specify the

addresses within a page and are ignored during an erase

operation.

•

To write a single byte of data to EEPROM. In this case, the

command byte is the high byte of the EEPROM address

from 0xF8 to 0xFB. The first data byte is the low byte of the

EEPROM address, and the second data byte is the actual

data, as shown in Figure 37.

SLAVE

ADDRESS

EEPROM

ADDRESS

HIGH BYTE

(0xF8 TO 0xFB)

SW A

EEPROM

ADDRESS

LOW BYTE

(0x00 TO 0xFF)

DATA

Figure 37. Single Byte Write to EEPROM

Block Write

In a block write operation, the master device writes a block of

data to a slave device. The start address for a block write must

have been set previously. In the ADM1067, a send byte opera-

tion sets a RAM address, and a write byte/word operation sets

an EEPROM address, as follows:

The master device asserts a start condition on SDA.

The master sends the 7-bit slave address followed by

the write bit (low).

The addressed slave device asserts ACK on SDA.

The master sends a command code that tells the slave

device to expect a block write. The ADM1067 command

code for a block write is 0xFC (1111 1100).

The slave asserts ACK on SDA.

The master sends a data byte that tells the slave device how

many data bytes are being sent. The SMBus specification

allows a maximum of 32 data bytes in a block write.

The slave asserts ACK on SDA.

The master sends N data bytes.

The slave asserts ACK on SDA after each data byte.

10. The master asserts a stop condition on SDA to end the

transaction.

SLAVE

ADDRESS

SW A

COMMAND 0xFC

(BLOCK WRITE)

BYTE

COUNT

A P

DATA

Figure 38. Block Write to EEPROM or RAM

Unlike some EEPROM devices that limit block writes to within

a page boundary, there is no limitation on the start address

when performing a block write to EEPROM, except when

•

There must be at least N locations from the start address to

the highest EEPROM address (0xFBFF), to avoid writing to

invalid addresses.

•

An addresses cross a page boundary. In this case, both

pages must be erased before programming.

Note that the ADM1067 features a clock extend function for

writes to EEPROM. Programming an EEPROM byte takes

approximately 250 μs, which limits the SMBus clock for repeated

or block write operations. The ADM1067 pulls SCL low and

extends the clock pulse when it cannot accept any more data.

READ OPERATIONS

The ADM1067 uses the following SMBus read protocols.

Receive Byte

In a receive byte operation, the master device receives a single

byte from a slave device, as follows:

The master device asserts a start condition on SDA.

The master sends the 7-bit slave address followed by the

read bit (high).

The addressed slave device asserts ACK on SDA.

The master receives a data byte.

The master asserts no acknowledge on SDA.

The master asserts a stop condition on SDA, and the

transaction ends.

In the ADM1067, the receive byte protocol is used to read a

single byte of data from a RAM or EEPROM location whose

address has previously been set by a send byte or write

byte/word operation, as shown in Figure 39.

SLAVE

ADDRESS

DATA

Figure 39. Single Byte Read from EEPROM or RAM

Block Read

In a block read operation, the master device reads a block of

data from a slave device. The start address for a block read must

have been set previously. In the ADM1067, this is done by a

send byte operation to set a RAM address, or a write byte/word

operation to set an EEPROM address. The block read operation

itself consists of a send byte operation that sends a block read

command to the slave, immediately followed by a repeated start

and a read operation that reads out multiple data bytes, as

follows:

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