MSAN-128 Zarlink Semiconductor, Inc., MSAN-128 Datasheet - Page 2

• Manufacturer Part Number: MSAN-128
• Description: Implementing an ISDN Architecture Using the ST-BUS
• Manufacturer: Zarlink Semiconductor, Inc.

A s c a n b e s e e n f r o m F i g u r e 1 , t h e r e a r e p o i n t s i n
theend-to-end transmission of information through
anISDN, where information must change from one
typeof transmission scheme to another. These points
a r e a t t h e T e r m i n a l E q u i p m e n t ( T E ) , t h e
NetworkTerminations (NT), the Loop Terminations
(LT), theExchange Termination (ET) etc., shown in
Figure 1.Rather than create a different interface
componentfor each unique type of carrier-to-carrier
transition, itis more practical to design an interface
betweeneach type of transmission method and
someintermediate format.
T h e i n t e r m e d i a t e f o r m a t c a l l e d f o r i s a
commonmechanism to transfer information between
theinterface devices. The ST-BUS, developed by
Zarlink Semiconductor, is a component interface
d e s i g n e d s p e c i fi c a l l y f o r t h i s p u r p o s e .
application notedescribes the ST-BUS structure as it
a p p l i e s t o b o t h t h e I S D N m o d e l a n d t h e I S D N
componentsdeveloped by Zarlink Semiconductor.
The electricalspecification for the ST-BUS may be
found in ZarlinkSemiconductor’s data book.
2.0ISDN Information Channels
Information travels on ISDN transmission media inthe
f o r m o f s e r i a l d i g i t a l d a t a s t r e a m s .
E a c h i n f o r m a t i o n s t r e a m c a n s u p p o r t
m u l t i p l e c o m m u n i c a t i o n
Time DivisionMultiplexing (TDM).
has defined several
A-136
BIT CELLS
4096 kHz
Clock
Frame Pulse
ST-BUS
Channel
0
Channel 31
Bit 0
Channel
1
Figure 3 - Clock & Frame Alignment for ST-BUS Streams
c h a n n e l s
Bit 7
Channel
Channel 0
Bit 7
2
Figure 2 - ST-BUS Stream Format
Bit 6
The CCITT
125 µs
t h r o u g h
Bit 5
• • •
T h i s
Channel 0
Bit 6
Bit 6
types of information channels, each with a defined
bitrate.
Signalling information, telemetry information and
lowspeed packet communications are carried on D-
c h a n n e l s , w h i c h h a v e a b i t r a t e o f 1 6 k b i t / s
(D(16))and a bit rate of 64 kbit/s (D(64)). Information
thatwill be termed “user information” in this note,
i s c a r r i e d o n B - c h a n n e l s , H 0 - c h a n n e l s , H 1 1 -
channelsand H12-channels. This information can be
c i r c u i t s w i t c h e d d a t a , p a c k e t s w i t c h e d d a t a ,
audio,facsimile,
T h e b i t r a t e s f o r u s e r i n f o r m a t i o n c h a n n e l s a r e a s
follows:
a)
b)
c)
d)
T h e i n t e r f a c e b e t w e e n I S D N c o m p o n e n t s
m u s t s u p p o r t
informationchannels.
therefore, mustuse TDM techniques, based on the 64
kbit/s channelrate common to all channel types.
Multiple 64 kbit/schannels can be used to construct the
h i g h e r b a n d w i d t h H 0 , H 1 1 a n d H 1 2 - c h a n n e l s .
At the 16kbit/s rate, the data fits into two bits of a 64
kbit/schannel.The maximum throughput supported by
the currentrecommendations is 2048 kbit/s (32X64
kbit/s
(8/2048) ms
Bit 3
B-channel :
H0-channel :
H11-channel :
H12-channel :
Channel
Bit 2
Channel 0
30
Bit 5
a l l
Bit 1
telex
Channel
64 kbit/s
384 kbit/s
1536 kbit/s
1920 kbit/s
t h e
31
The component interface,
Bit 0
or
Application Note
d i f f e r e n t
Channel 0
Channel
Bit 4
video
0
information.
t y p e s
o f