FTR-1621-XX WDM GBIC
Product Specification - March 2002
Finisar
VIII. Serial Communication Protocol
All Finisar optical GBICs are ‘Module Definition “4”’ and support the 2 wire serial
communication protocol outlined in the GBIC Specification
1
. These GBICs use an
Atmel AT24C01A 128 byte E
2
PROM (with an address of 1010000X). For details on
interfacing with the E
2
PROM, see the Atmel data sheet titled “AT24C01A/02/04/08/16 2-
Wire Serial CMOS E
2
PROM.”
5
All Finisar optical GBICs also incorporate a microcontroller that monitors system
parameters such as laser current, laser temperature, and, in the case of
13xx/14xx/15xx/16xx nm parts, transmitted power. For a complete description of how to
use Finisar’s extended features, see Finisar’s Application Note AN-2030
4
.
CAUTION:
The microcontroller implements the Philips I
2
C protocol including clock stretching. For
details, consult the Philips I
2
C-Bus Specification. Clock stretching allows a fast master to communicate
with a slow slave device, and it requires that the host monitor the clock line every time it releases the line
high. If a host does not implement clock stretching (drives the bus blind), it must run the clock below
8kHz, so that Finisar’s microcontroller has time to process instructions. If clock stretching is supported, the
clock may be run at up to 100kHz.
I
2
C Timing Requirements
Parameter
Atmel I
2
C Clock Rate
Finisar Microcontroller
I
2
C Clock Rate
Finisar Microcontroller
I
2
C Clock Rate
Symbol
C
atmel
C
1
Min
0
10
Typ
Max
100,000
100,000
Units Notes/Conditions
Hz Bus can be driven blind.
Hz
Host must support clock stretching.
Microcontroller times out if C <
10Hz.
Bus can be driven blind.
Microcontroller times out if C <
10Hz.
C
2
10
8000
Hz
Table 9. I
2
C timing requirements
© Finisar Corporation 01-Mar-02 Rev.F
Page 7
FINISAR [ FINISAR CORPORATION. ]
