Optical Transceivers
Design Reference Guide
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Page 3
10/2014
LOW SPEED ELECTRICAL HARDWARE PINS
In addition to the 2-wire serial interface the XFP module has the following low speed pins for control and status:
Mod_NR Mod_DeSel Interrupt TX_DIS
Mod _ABS RX_LOS P_Down/RST.
MOD_NR
The Mod_NR is an output pin that when High, indicates that the module has detected a condition that renders
transmitter and or receiver data in-valid, shall consist of logical OR of the following signals:
•Transmit Signal Conditioner Loss of Lock
•Transmitter Laser Fault
•Receiver Signal Conditioner Loss of Lock
Other conditions deemed valuable to the detection of fault may be added to the Mod_NR. The Mod_NR
output pin is an open collector and must be pulled to Host_Vcc on the host board.
MOD_DESEL
The Mod_DeSel is an input pin. When held Low by the host, the module responds to 2-wire serial communication
commands. The Mod_DeSel allows the use of multiple XFP modules on a single 2-wire interface bus. When the
Mod_DeSel pin is “High”, the module shall not respond to or acknowledge any 2-wire interface communication
from the host. Mod_DeSel pin must be pulled to VCC3 in the module.
In order to avoid conflicts, the host system shall not attempt 2-wire inter-face communications within the
Mod_DeSel assert time after any XFP modules are deselected. Similarly, the host must wait at least for the pe-riod
of the Mod_DeSel deassert time before communicating with the newly selected module. The assertion and de-
assertion periods of dif-ferent modules may overlap as long as the above timing requirements are met.
INTERRUPT
Interrupt is an output pin. When “Low”, indicates possible module operational fault or a status critical to the host
system. The Interrupt pin is an open collector output and must be pulled up to Host_Vcc the host board.
TX_DIS
TX_DIS is an input pin. When TX_DIS is asserted High, the XFP module transmitter output must be turned off. The
TX_DIS pin must be pulled up to VCC3 in the XFP module.
MOD_ABS
Mod_ABS is pulled up to Host_Vcc on the host board and grounded in the XFP module. Mod_ABS is then asserted
“High” when the XFP module is physically absent from a host slot.
RX_LOS
The RX_LOS when High indicates insufficient optical power for reliable signal reception. The RX_LOS pin is an
open collector output and must be pulled up to Host_Vcc on the host board.
