ADM1026
1
SCL
9
1
9
SDA
START BY
MASTER
0
1
0
1
1
A1
A0
R/W
ACK. BY
SLAVE
D7
D6
D5
D4
D3
D2
D1
D0
ACK. BY
SLAVE
FRAME 1
SLAVE ADDRESS
1
SCL
(CONTINUED)
9
1
FRAME 2
COMMAND CODE
9
SDA
(CONTINUED)
D7
D6
D5
D4
D3
D2
D1
D0
ACK. BY
SLAVE
D7
D6
D5
D4
D3
D2
D1
D0
ACK. BY
SLAVE
STOP BY
MASTER
02657-A-017
FRAME 3
DATA BYTE
FRAME N
DATA BYTE
Figure 17. General SMBus Write Timing Diagram
1
SCL
9
1
9
SDA
START BY
MASTER
0
1
0
1
1
A1
A0
R/W
ACK. BY
SLAVE
D7
D6
D5
D4
D3
D2
D1
D0
ACK. BY
MASTER
FRAME 1
SLAVE ADDRESS
1
SCL
(CONTINUED)
9
1
FRAME 2
DATA BYTE
9
SDA
(CONTINUED)
D7
D6
D5
D4
D3
D2
D1
D0
ACK. BY
MASTER
D7
D6
D5
D4
D3
D2
D1
D0
NO ACK.
STOP BY
MASTER
02657-A-018
FRAME 3
DATA BYTE
FRAME N
DATA BYTE
Figure 18. General SMBus Read Timing Diagram
SMBus PROTOCOLS FOR RAM AND EEPROM
The ADM1026 contains volatile registers (RAM) and non-
volatile EEPROM. RAM occupies Addresses 00h to 6Fh, while
EEPROM occupies Addresses 8000h to 9FFFh.
Data can be written to and read from both RAM and EEPROM
as single data bytes and as block (sequential) read or write
operations of 32 data bytes, the maximum block size allowed by
the SMBus specification.
Data can only be written to unprogrammed EEPROM locations.
To write new data to a programmed location, it is first necessary
to erase it. EEPROM erasure cannot be done at the byte level;
the EEPROM is arranged as 128 pages of 64 bytes, and an entire
page must be erased. Note that of these 128 pages, only 124
pages are available to the user. The last four pages are reserved
for manufacturing purposes and cannot be erased/rewritten.
The EEPROM has three RAM registers associated with it,
EEPROM Registers 1, 2, and 3 at Addresses 06h, 0Ch, and 13h.
EEPROM Registers 1 and 2 are for factory use only. EEPROM
Register 3 sets up the EEPROM operating mode. Setting Bit 0 of
EEPROM Register 3 puts the EEPROM into read mode. Setting
Bit 1 puts it into programming mode. Setting Bit 2 puts it into
erase mode.
Only one of these bits must be set before the EEPROM may be
accessed. Setting no bits or more than one of them causes the
device to respond with No Acknowledge if an EEPROM read,
program, or erase operation is attempted.
It is important to distinguish between SMBus write opera-
tions, such as sending an address or command, and EEPROM
programming operations. It is possible to write an EEPROM
address over the SMBus, whatever the state of EEPROM
Register 3. However, EEPROM Register 3 must be correctly set
before a subsequent EEPROM operation can be performed. For
example, when reading from the EEPROM, Bit 0 of EEPROM
Register 3 can be set, even though SMBus write operations are
required to set up the EEPROM address for reading.
Rev. A | Page 13 of 56
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