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IXF1104 4-Port Gigabit Ethernet Media Access Controller
Datasheet 114
Document Number: 278757
Revision Number: 009
Revision Date: 27-Oct-2005
5.7.3.6.3 Acknowledge
All addresses and data words are serially transmitted to and from the optical module in 8-bit words.
The optical module E²PROM sends a zero to acknowledge that it has received each word, which
happens during the ninth clock cycle (see Figure 27).
5.7.3.6.4 Memory Reset
After an interruption in protocol, power loss, or system reset, any 2-wire optical module can be
reset by following three steps:
1. Clock up to 9 cycles
2. Wait for I
2
C_DATA High in each cycle while I
2
C_CLK is High
3. Initiate a start condition.
5.7.3.6.5 Device Addressing
All E²PROMs in SFP optical module devices require an 8-bit device address word following a start
condition to enable the chip to read or write. The device address word consists of a mandatory one,
zero sequence for the four most-significant bits. This is common to all devices. The next three bits
are the A2, A1, and A0 device address bits that are tied to zero in an optical module. The eighth bit
of the device address is the Read/Write operation select bit. A Read operation is initiated if this bit
is High and a Write operation is initiated if this bit is Low.
Upon comparison of the device address, the optical module outputs a zero. If a comparison is not
made, the optical module E²PROM returns to a standby state.
5.7.3.6.6 Random Read Operation
A random Read requires a “dummy” Byte/Write sequence to load the data word address. The
“dummy” write is achieved by first sending the device address word with the Read/Write bit
cleared to Low, which signals a Write operation. The optical module acknowledges receipt of the
device address word. The IXF1104 MAC sends the data word address, which is again
acknowledged by the optical module. The IXF1104 MAC generates another start condition. This
completes the “dummy” write and sets the optical module E²PROM pointers to the desired
location.
Figure 27. Acknowledge Timing
START ACKNOWLEDGE
I
2
C_Data
DATA IN
DATA OUT