MSAN-128 Zarlink Semiconductor, Inc., MSAN-128 Datasheet - Page 9

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

Application Note
The ST-BUS control/status channel is visible from
the microprocessor port, so that the control/status
channel of either the MT8930 or the MT8972 may be
accessed. The ST-BUS channel allocation of the
MT8994/5 is programmable, so other ST-BUS ISDN
components can share the B channels of the
transmission device with the D-Phone.
A potential TE other than a TE1 could consist of an
MT8994/5, MT8952B HDLC controller and an
MT8972 (Figure 9). This would be equivalent to a
TE1 incorporating the NT1 function. The MT8952B
would provide protocolled control over the D-channel
or over either B-channel (for interworking with packet
networks), while the MT8994/5 provides voice
communication over either B-channel.
4.6 Link Layer Support
Recommendation I.441 specifies the User/Network
data link layer protocol for ISDN.
specified in I.441 is called Link Access Procedure on
the D-Channel (LAPD).
information, as well as telemetry information and low
rate packet communications, is transferred across
the D-channel in LAPD formatted packets.
LAPD is very similar to the High Level Data-Link
Control (HDLC) protocol and the LAPB protocol that
is
Differences between these protocols are limited to
procedural (or peer to peer) functions.
functions, such as opening and closing flags, data
transparency through bit stuffing and Frame Check
Sequence calculation, are all common among
protocols like HDLC, LAPD, and LAPB.
The fact that the PA/D function is common among
many layer 2 protocols makes the MT8952B HDLC
specified
Handset
Hands
in
Free
CCITT
Figure 9 - TE1 Connected Directly to U Reference Point
recommendation
All ISDN signalling
The protocol
MT8994/5
C
DSTo
DSTi
X.25.
C4i
PA/D
F0i
Controller (a PA/D device) useful in a variety of
network functions. It can be used as a D-channel
communication device, or it can be used for
interworking with non-ISDN packet networks, such
as an X.25 network, through a B-channel. It has a
microprocessor port and and ST-BUS port, allowing
it to be used with any combination of ST-BUS ISDN
components, as shown in Figure 9.
The ST-BUS clock signals required by the MT8952B
are a frame pulse and 4096 kHz clock (or optionally
2048 kHz). Information transfer rates supported are
8 kbit/s, 16 kbit/s, 48 kbit/s, 56 kbit/s, 64 kbit/s, 128
kbit/s and 192 kbit/s.
positions are compatible with the D-channel and B-
channel positions of the MT8972 and the MT8930.
Transfer rates of 8, 16, and 48 kbit/s are only
available
compatibility). With a 64 kbit/s transfer rate, data is
available on either channel 2, 3 or 4, where channels
2 and 3 are compatible with the B-channel. At the
128 kbit/s transfer rate, data is concatenated on
channels 2 and 3 and at 192 kbit/s data is
concatenated on channels 2, 3 and 4 (this last option
is not useful for basic rate applications). ST-BUS
channel 1 is dedicated to a special register in the
MT8952B, meant to map directly into the control/
status channels of the basic rate components.
The MT8952B is designed for use with the MT8972
and as a component to be used as part of a larger,
central signalling resource.
favour a loosely coupled approach to signalling and
control, separate from transmission facilities. On the
other hand, TE applications favour a signalling
resource tightly coupled to the transmission circuitry.
The PA/D function is built into the MT8930 for TE
applications.
ST-BUS
through
C4i
F0i
DSTi
DSTo
DSTi
DSTo
F0/CLD
C4/TCK
MT8952B
MT8972
(PA/D)
channel
Bit positions and channel
Network applications
MSAN-128
0
U
(D
channel
A-143