ADM1065ASUZ datasheet(23/28 Pages) AD

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ADM1065

Rev. D | Page 23 of 28

SMBus PROTOCOLS FOR RAM AND EEPROM

The ADM1065 contains volatile registers (RAM) and nonvolatile

registers (EEPROM). User RAM occupies Address 0x00 to

Address 0xDF; the EEPROM occupies Address 0xF800 to

Address 0xFBFF.

Data can be written to and read from both the RAM and the

EEPROM as single data bytes. Data can be written only to

unprogrammed EEPROM locations. To write new data to

a programmed location, the location contents must first be

erased. EEPROM erasure cannot be done at the byte level. The

EEPROM is arranged as 32 pages of 32 bytes each, and an entire

page must be erased.

Page erasure is enabled by setting Bit 2 in the UPDCFG register

(Address 0x90) to 1. If this bit is not set, page erasure cannot

occur, even if the command byte (0xFE) is programmed across

the SMBus.

WRITE OPERATIONS

The SMBus specification defines several protocols for different

types of read and write operations. The following abbreviations

are used in Figure 29 to Figure 37:

•

S = Start

•

P = Stop

•

R = Read

•

W = Write

•

A = Acknowledge

•

A = No acknowledge

The ADM1065 uses the following SMBus write protocols.

Send Byte

In a send byte operation, the master device sends a single

command byte to 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 write bit (low).

The addressed slave device asserts an acknowledge (ACK)

on SDA.

The master sends a command code.

The slave asserts an ACK on SDA.

The master asserts a stop condition on SDA and

the transaction ends.

In the ADM1065, the send byte protocol is used for two purposes:

•

To write a register address to the RAM for a subsequent

single byte read from the same address or for a block read

or a block write starting at that address, as shown in Figure 29.

SLAVE

ADDRESS

RAM

ADDRESS

(0x00 TO 0xDF)

Figure 29. Setting a RAM Address for Subsequent Read

•

To erase a page of EEPROM memory. EEPROM memory

can be written to only if it is unprogrammed. Before writing

to one or more EEPROM memory locations that are already

programmed, the page(s) containing those locations must

first be erased. EEPROM memory is erased by writing a

command byte.

The master sends a command code telling the slave device to

erase the page. The ADM1065 command code for a page

erasure is 0xFE (1111 1110). Note that for a page erasure to

take place, the page address must be given in the previous

write word transaction (see the Write Byte/Word section).

In addition, Bit 2 in the UPDCFG register (Address 0x90)

must be set to 1.

SLAVE

ADDRESS

COMMAND

BYTE

(0xFE)

Figure 30. EEPROM Page Erasure

As soon as the ADM1065 receives the command byte,

page erasure begins. The master device can send a stop

command as soon as it sends the command byte. Page

erasure takes approximately 20 ms. If the ADM1065 is

accessed before erasure is complete, it responds with

a no acknowledge (NACK).

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