ADM1069ASTZ datasheet(29/32 Pages) AD

29 / 32 page

ADM1069

Rev. C | Page 29 of 32

Write Byte/Word

In a write byte/word operation, the master device sends a

command byte and one or two data bytes to the slave device,

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 an ACK on SDA.

The master sends a command code.

The slave asserts an ACK on SDA.

The master sends a data byte.

The slave asserts an ACK on SDA.

The master sends a data byte (or asserts a stop condition).

The slave asserts an ACK on SDA.

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

transaction.

In the ADM1069, the write byte/word protocol is used for the

following three purposes:

•

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

command byte is RAM Address 0x00 to RAM Address 0xDF,

and the only data byte is the actual data, as shown in Figure 41.

SLAVE

ADDRESS

RAM

ADDRESS

(0x00 TO 0xDF)

W A

DATA

Figure 41. Single Byte Write to the RAM

•

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

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

the command byte is the high byte of EEPROM Address 0xF8

to EEPROM Address 0xFB. The only data byte is the low byte

of the EEPROM address, as shown in Figure 42.

SLAVE

ADDRESS

EEPROM

ADDRESS

HIGH BYTE

(0xF8 TO 0xFB)

SW A

EEPROM

ADDRESS

LOW BYTE

(0x00 TO 0xFF)

Figure 42. Setting an EEPROM Address

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

the address low byte are important for 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 the EEPROM. In this case, the

command byte is the high byte of EEPROM Address 0xF8

to EEPROM Address 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 43.

SLAVE

ADDRESS

EEPROM

ADDRESS

HIGH BYTE

(0xF8 TO 0xFB)

SW A

EEPROM

ADDRESS

LOW BYTE

(0x00 TO 0xFF)

DATA

Figure 43. Single Byte Write to the 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 ADM1069, 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 an ACK on SDA.

The master sends a command code that tells the slave

device to expect a block write. The ADM1069 command

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

The slave asserts an 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 an ACK on SDA.

The master sends N data bytes.

The slave asserts an 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

910

A P

DATA

Figure 44. Block Write to the 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 are fewer than N locations from the start address to

the highest EEPROM address (0xFBFF), which results in

writing to invalid addresses.

•

An address crosses a page boundary. In this case, both

pages must be erased before programming.

Note that the ADM1069 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 ADM1069 pulls SCL

low and extends the clock pulse when it cannot accept any

more data.

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