Datasheet

ADM1069
Rev. C | Page 29 of 32
8
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 an ACK on SDA.
4.
The master sends a command code.
5.
The slave asserts an ACK on SDA.
6.
The master sends a data byte.
7.
The slave asserts an ACK on SDA.
8.
The master sends a data byte (or asserts a stop condition).
9.
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.
04735-041
SLAVE
ADDRESS
RAM
ADDRESS
(0x00 TO 0xDF)
S W A DATAAPA
2413 576
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.
04735-042
SLAVE
ADDRESS
EEPROM
ADDRESS
HIGH BYTE
(0xF8 TO 0xFB)
SWA
EEPROM
ADDRESS
LOW BYTE
(0x00 TO 0xFF)
APA
2413 5 76 8
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.
04735-043
SLAVE
ADDRESS
EEPROM
ADDRESS
HIGH BYTE
(0xF8 TO 0xFB)
SWA
EEPROM
ADDRESS
LOW BYTE
(0x00 TO 0xFF)
APA
2413 5 7
A
9
DATA
86 10
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:
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 ACK on SDA.
4.
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).
5.
The slave asserts an ACK on SDA.
6.
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.
7.
The slave asserts an ACK on SDA.
8.
The master sends N data bytes.
9.
The slave asserts an ACK on SDA after each data byte.
10.
The master asserts a stop condition on SDA to end the
transaction.
04735-044
SLAVE
ADDRESS
SWA
2
COMMAND 0xFC
(BLOCK WRITE)
413
A
5
BYTE
COUNT
6
A
7
A
910
A PA
DATA
1
8
DATA
N
DATA
2
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.