SMSC LAN9312 - Manual (Page 143)

High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
SMSC LAN9312 143 Revision 1.4 (08-19-08)
DATASHEET
Sequential reads are used by the EEPROM Loader. Refer to Section 10.2.4, "EEPROM Loader" for
additional information.
For a register level description of a read operation, refer to Section 10.2.1, "EEPROM Controller
Operation," on page 138 .
10.2.2.5 I
2
C EEPROM Byte Writes
Following the device addressing, a data byte may be written to the EEPROM by outputting the data
after receiving the acknowledge from the EEPROM. The data byte is acknowledged by the EEPROM
slave and the I
2 C master finishes the write cycle with a stop condition. If the EEPROM slave fails to
send an acknowledge, then the sequence is aborted and the EPC_TIMEOUT bit in the EEPROM
Command Register (E2P_CMD) is set.
Following the data byte write cycle, the I 2 C master will poll the EEPROM to determine when the byte
write is finished. A start condition is sent followed by a control byte with a control code of 1010b,
chip/block select bits low, and the R/~W bit low. If the EEPROM is finished with the byte write, it will
respond with an acknowledge. Otherwise, it will respond with a no-acknowledge and the I
2
C master
will repeat the poll. If the acknowledge does not occur within 30mS, a time-out occurs. Once the I
2
C
master receives the acknowledge, it concludes by sending a start condition, followed by a stop
condition, which will place the EEPROM into standby.
Figure 10.4 illustrates typical I
2
C EEPROM byte write.
For a register level description of a write operation, refer to Section 10.2.1, "EEPROM Controller
Operation," on page 138 .
Figure 10.6 I 2 C EEPROM Byte Write
A
C
K
Data Byte
P
A
C
K
S 1 0 1 0 0
Control Byte
0 0 0 S 1 0 1 0 0 0 0 0 S 1 0 1 0 0 0 0 0
...
D
7 D
6 D
5 D
4 D
3
D
2
D
1 D
0 A
C
K A
C
K
A
C
K
S P
Poll Cycle Poll Cycle Poll Cycle Data Cycle
Conclude
R/~W Chip / Block
Select Bits
R/~W Chip / Block
Select Bits
R/~W Chip / Block
Select Bits
Control Byte Control Byte