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ADM1168 Datasheet PDF : 27 Pages
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ADM1168
SMBus PROTOCOLS FOR RAM AND EEPROM
The ADM1168 contains volatile registers (RAM) and nonvolatile
registers (EEPROM). User RAM occupies Address 0x00 to
Address 0xDF; and 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 28 to Figure 36:
S = Start
P = Stop
R = Read
W = Write
A = Acknowledge
A = No acknowledge
The ADM1168 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:
1. The master device asserts a start condition on SDA.
2. The master sends the 7-bit slave address followed by the
write bit (low).
3. The addressed slave device asserts an acknowledge (ACK)
on SDA.
4. The master sends a command code.
5. The slave asserts ACK on SDA.
6. The master asserts a stop condition on SDA and the
transaction ends.
In the ADM1168, 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 28.
1
2
S
SLAVE
ADDRESS
3
WA
4
RAM
ADDRESS
(0x00 TO 0xDF)
56
AP
Figure 28. Setting a RAM Address for Subsequent Read
Data Sheet
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 ADM1168 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. See Figure 29.
1
2
3
S
SLAVE
ADDRESS
WA
4
COMMAND
BYTE
(0xFE)
56
AP
Figure 29. EEPROM Page Erasure
As soon as the ADM1168 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 ADM1168 is
accessed before erasure is complete, it responds with a
no acknowledge (NACK).
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:
1. The master device asserts a start condition on SDA.
2. The master sends the 7-bit slave address followed by the
write bit (low).
3. The addressed slave device asserts ACK on SDA.
4. The master sends a command code.
5. The slave asserts ACK on SDA.
6. The master sends a data byte.
7. The slave asserts ACK on SDA.
8. The master sends a data byte or asserts a stop condition.
9. The slave asserts ACK on SDA.
10. The master asserts a stop condition on SDA to end the
transaction.
In the ADM1168, the write byte/word protocol is used for 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 30.
1
2
3
4
5 6 78
S
SLAVE
ADDRESS
W
A
RAM
ADDRESS
(0x00 TO 0xDF)
A
DATA
AP
Figure 30. Single Byte Write to the RAM
Rev. B | Page 24 of 27
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