FTLF8524E2xNy 2x7 Pin SFF Product Specification – July 2005
VIII. Digital Diagnostic Functions
Finisar FTLF8524E2xNy 2x7 SFF transceivers support a 2-wire serial communication
protocol. This interface is identical to the 2-wire serial interface defined in the SFP
MSA
4
, however in this case it is implemented on the 2x7 SFF form factor.
The standard SFP serial ID provides access to identification information that describes
the transceiver’s capabilities, standard interfaces, manufacturer, and other information.
Additionally, an enhanced digital diagnostic monitoring interface is defined, which
allows real-time access to device operating parameters such as transceiver temperature,
laser bias current, transmitted optical power, received optical power and transceiver
supply voltage. It also defines a sophisticated system of alarm and warning flags, which
alerts end-users when particular operating parameters are outside of a factory set normal
range.
In order to access the identification information, the 2x7 SFF transceivers have a 256-
byte memory map in E
2
PROM that is accessible over a 2-wire serial interface at the 8 bit
address 1010000X (A0h). The digital diagnostic monitoring interface makes use of the 8
bit address 1010001X (A2h), so the originally defined serial ID memory map remains
unchanged. The interface is identical to, and is thus fully backward compatible with both
the GBIC Specification and the SFP Multi Source Agreement. Additional information,
including details of the electronic interface, is described in Finisar Application Note AN-
2030: “Digital Diagnostics Monitoring Interface for SFP Optical Transceivers”.
The operating and diagnostics information is monitored and reported by a Digital
Diagnostics Transceiver Controller (DDTC) inside the transceiver, which is accessed
through a 2-wire serial interface. When the serial protocol is activated, the serial clock
signal (SCL, Mod Def 1) is generated by the host. The positive edge clocks data into the
2x7 SFF transceiver into those segments of the E
2
PROM that are not write-protected.
The negative edge clocks data from the 2x7 SFF transceiver. The serial data signal
(SDA, Mod Def 2) is bi-directional for serial data transfer. The host uses SDA in
conjunction with SCL to mark the start and end of serial protocol activation. The
memories are organized as a series of 8-bit data words that can be addressed individually
or sequentially.
For more information, please see the SFP MSA documentation
4,5
and Finisar Application
Note AN-2030.
One difference in the implementation of digital diagnostics in the SFF 2x7 form factor
from the SFP MSA documentation is the readout of Bit 1, Byte 110 at Address A2h
(called “Digital State of the LOS output pin” in the SFP documentation). In the SFF 2x7,
the output of this bit is inverted to indicate Signal Detect and match the output of the
Signal Detect pin on the SFF part.
Digital diagnostics for the FTLF8524E2xNy can be used in host systems that require
either internally or externally calibrated digital diagnostics.
Finisar Corporation July 12, 2005 RevG
Page 6
FINISAR [ FINISAR CORPORATION. ]
