~ National ~ Semiconductor - Al Kossow's Bitsavers

NSC Solutions: Systems Level
Basic Access Line Cards
'S' OR 'u' JII
RErERENCE
POINT
r---~ ........... ---+ BACKPLANE
TP3400
TP341 0
TP3420
For operation on a line card in a C.O., PABX or NT-2, each
of the 3 transceiver devices can be set to operate as the
timing master for the loop, being synchronized to the system
clock and controlling all loop frame timing. If programmable
time-slot assignment is required, the TP3155 TSAC
provides 8 individually programmable frame sync pulse outputs
locked to a common frame marker. 'B' channels can be
interfaced to standard backplane interfaces, while 'D' channels
can be either multiplexed on and off the card for processing
or can undergo Layer 2 processing on the card itself.
For the latter method, one HPC16400 handles Layer 2 framing
for 2 basic access lines. In this manner, packets are first
identified as data or signalling type by analysis of the SAPI
field, with data packets being routed separately to a packet
switch access node. If required, signalling packets can undergo
protocol conversion in the HPC to an existing internal
switch control protocol.
RErERENCE
'S' OR 'U'
POINT
JII
TP3400
TP341 0
TP3420
TLiX/0008-6
Building an NT-1
An NT-1 Network Termination is defined as a Layer 1 device
only, which converts the 2-wire long-haul 'U' interface to the
limited distance 4-wire 'S' interface. It has no capability for
intercepting higher layers of the 'D' channel protocol. As
such, it is built simply by connecting a TP3420 SID, configured
in NT (or Master) mode, to a TP3410 Echo-canceller
operating in Slave mode. Sharing a common 15.36 MHz
JII
JII
1
'S'
TP3420
"SID"
MICROWIRE
COP413C
(OPTIONAL FOR LAYER
# 1 MAINTENANCE)
crystal, these devices pass 'B' and 'D' channel information
across the standard 4-wire interface. Layer 1 maintenance
protocols across both the 'U' and the 'SIT' interfaces,
which are as of yet not definitively specified by most adminstrations,
may be handled by a low cost 4-Bit COPSTM
Microcontroller via its Microwire Interface.
TP341 0
E-C
lie
1
'U'
TL/X/0008-7
3-7