8-2
ISDN and 16-bit Audio
ISDN Overview
8.1
ISDN Overview
The integrated services digital network (ISDN) is an advanced telephone
system which allows computers to communicate together at a higher data
rate than they could using a modem. Information carried on the ISDN is
digital and uses a circuit switched system at a basic rate of 64 KB/s on each
of two bearer channels, or B channels, and 16 KB/s on a signaling and
control channel, or D channel. The B channels can be combined to provide
a maximum throughput of 128 KB/s.
The ISDN interface on SPARCbook 3 provides a 4-wire terminal endpoint
(TE) connection via an RJ45 connector on the I/O panel, providing transmit
and receive differential signal pairs. This is connected to the ISDN at the S
(or S/T) interface point. Signals at the S point are then converted by an
adapter called a network termination (NT1) to use the more common two
wire telephone connection for which most premises are currently wired.
The connection can be point to point between an NT1 and TE or multipoint,
with up to eight TE devices attached to a single NT1. These eight devices
may share a single ISDN line to achieve virtually simultaneous operation.
Time division multiplexing is employed to superimpose both B channels
and D channel together onto a differential wire pair. The data carried on the
B channels is arbitrary and could contain digitized voice and picture
information, or raw computer data. A collision detection and backoff
strategy allows multiple TEs to share the D channel for control and
signaling functions.
Basic rate ISDN uses a 48-bit frame and defines several time slots within
the frame. Among these are the D channel and two B channels. There are
additional bits of information which are required by the physical layer
electronic circuits to support the framing, synchronization and multipoint
capabilities of ISDN.
8.2
DBRI Overview
The the AT&T T7259 Dual Basic Rate ISDN Controller (DBRI) functions
as a multiport tap into an ISDN line and has four ports through which data
is passed. In addition to the synchronous serial TE port, there is an NT port
(not used in SPARCbook 3), a serial Concentration Highway Interface
(CHI) port, and the 32-bit SBus DMA port. In general, the DBRI is a digital
data transport, formatter and multiplexer that dynamically routes bits
within time slots between ports.
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Содержание SPARCbook 3 series
Страница 1: ...Series Technical Reference Manual 980327 02 3 S3GX_TRMBook Page i Friday September 19 1997 11 39 am...
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Страница 28: ...1 16 Architecture Overview Microcontroller Subsystem S3GX_TRMBook Page 16 Friday September 19 1997 11 39 am...
Страница 44: ...2 16 The SPARC CPU SBus Controller S3GX_TRMBook Page 16 Friday September 19 1997 11 39 am...
Страница 76: ...5 8 SCSI Controller DMA Support S3GX_TRMBook Page 8 Friday September 19 1997 11 39 am...
Страница 82: ...6 6 Ethernet Interface DMA Support for Network Operations S3GX_TRMBook Page 6 Friday September 19 1997 11 39 am...
Страница 96: ...7 14 PCMCIA Interface Microcontroller Registers S3GX_TRMBook Page 14 Friday September 19 1997 11 39 am...
Страница 146: ...9 28 MODEM Class 2 Fax Command Set S3GX_TRMBook Page 28 Friday September 19 1997 11 39 am...
Страница 180: ...11 30 Display Interface RAMDAC S3GX_TRMBook Page 30 Friday September 19 1997 11 39 am...
Страница 210: ...B 10 Connector Information Removable Hard Drive SCSI Connector S3GX_TRMBook Page 10 Friday September 19 1997 11 39 am...
Страница 216: ...Index vi S3GX_TRMBook Page vi Friday September 19 1997 11 39 am...