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4.2 Physical Layer Conversion
The primary function of the MOST50 E-O Converter is network signal conversion between electrical and
optical physical layers. The E-O Converter incorporates two OS81082
Intelligent Network Interface Controllers
(INICs) to achieve this conversion. The network frame rate of both ePHY and optical physical layer net-
works is 48 kHz. One INIC receives the incoming ePHY network signal and retransmits it as the outgoing
optical physical layer network signal; the other INIC receives the incoming optical physical layer network
signal and retransmits it as the outgoing ePHY network signal. This ePHY to optical physical layer conver-
sion is accomplished by re-clocking the MOST50 network signal while maintaining data integrity.
The optical physical layer signal is a pseudo MOST50 interface that is based on
Positive Emitter Coupled
Logic
(PECL). Since the optical physical layer network produces no emissions and is isolated electrically, it
can be routed through the EMC chamber wall and connected to another E-O Converter, where it is con-
verted back to an ePHY network signal. The optical physical layer interface consists of a 1300 nm wave-
length optical physical layer transceiver with a SC duplex receptacle. This allows the signal to be
transmitted over multi-mode, 62.5/125
μ
m glass optical fiber cable for distances up to 50 m. The
MOST50 E-O Converters can be integrated into larger chambers without adding any significant delay to
the network.
The incoming ePHY and optical physical layer network signals are checked for coding errors and network
unlocks. Any time an ePHY network error occurs, the
ePHY Error
LED (red) is pulsed on. Any time an optical
physical layer network error occurs, the
Optical Error
LED (red) is pulsed on. A coding error is indicated by an
LED (
ePHY Error
or
Optical Error
) pulse length greater than 50 ms, while a network unlock event produces a
pulse length greater than 150 ms. ePHY network errors are also conveyed from the
Versatile Link
optical
transmitter (see Figure 4-2). A
Versatile Link
optical receiver, along with a plastic optical fiber (POF) cable
can be used to capture ePHY network errors that occur during testing. This is especially useful for auto-
mated
Bulk Current Injection
(BCI) and
Transverse Electromagnetic
(TEM) cell testing, outlined in Sections 5.2
and 5.3. The pulse lengths of the ePHY network errors transmitted from the
Versatile Link
optical transmitter
are the same as ePHY network errors on the
ePHY Error
LED.
P
o
w
e
r
C
h
a
rg
e
O
p
tic
a
l E
rr
o
r
e
P
H
Y
E
rr
o
r
ePHY
Error
Optical
Versatile Link transmitter
Figure 4-2: Versatile Link Transmitter (ePHY Error)
