sp3508 Exar Corporation, sp3508 Datasheet - Page 29

• Manufacturer Part Number: sp3508
• Description: Rugged 3.3v, 20mbps, 8 Channel Multiprotocol Tranciever With Programmable Dce/dte And Terminination Resistors
• Manufacturer: Exar Corporation

TERM_OFF FUNCTION
The SP3508 contains a TERM_OFF pin that dis-
ables all three receiver input termination networks
regardless of mode. This allows the device to be
used in monitor mode applications typically found
in networking test equipment.
The TERM_OFF pin internally contains a pull-
down device with an impedance of over 500kΩ,
which will default in a "ON" condition during
power-up if V.35 receivers enable line and the
SHUTDOWN mode from the decoder will disable
the termination regardless of TERM_OFF.
LOOPBACK FUNCTION
The SP3508 contains a LOOPBACK pin that
invokes a loopback path. This loopback path is
illustrated in Figure 50. LOOPBACK has an inter-
nal pull-up resistor that defaults to normal mode
during power up or if the pin is left floating. During
loopback, the driver output and receiver input
characteristics will still adhere to its appropriate
specifications.
DECODER AND D_LATCH FUNCTION
The SP3508 contains a D_LATCH pin that latches
the data into the D0, D1 and D2 decoder inputs. If
tied to a logic LOW ("0"), the latch is transparent,
allowing the data at the decoder inputs to propa-
gate through and program the SP3508 accord-
ingly. If tied to a logic HIGH ("1"), the latch locks
out the data and prevents the mode from changing
until this pin is brought to a logic LOW.
Date: 10/26/04
SP3508 Enhanced WAN Multi–Mode Serial Transceiver
29
There are internal pull-up devices on D0, D1 and
D2, which allow the device to be in SHUTDOWN
mode ("111") upon power up. However, if the
device is powered-up with the D_LATCH at a
logic HIGH, the decoder state of the SP3508 will
be undefined.
CTR1/CTR2 EUROPEAN COMPLIANCY
As with all of Sipex's previous multi-protocol
serial transceiver IC's the drivers and receivers
have been designed to meet all the requirements to
NET1/NET2 and TBR2 in order to meet CTR1/
CTR2 compliancy. The SP3508 is also tested in-
house at Sipex and adheres to all the NET1/2
physical layer testing and the ITU Series V speci-
fications before shipment. Please note that al-
though the SP3508, as with its predecessors, ad-
here to CRT1/CTR2 compliancy testing, any com-
plex or usual configuration should be double-
checked to ensure CTR1/CTR2 compliance. Con-
sult the factory for details.
© Copyright 2004 Sipex Corporation
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