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ADM1065ASUZ Datasheet(PDF) 23 Page - Analog Devices
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ADM1065ASUZ Datasheet(HTML) 23 Page - Analog Devices
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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
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 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.
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)
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.
(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
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.
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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