ISO 8482:1987
(Main)Information processing systems — Data communication — Twisted pair multipoint interconnections
Information processing systems — Data communication — Twisted pair multipoint interconnections
Systèmes de traitement de l'information — Communication de données — Interconnexions multipoints par paire torsadée
General Information
Relations
Standards Content (Sample)
[SO
3482
INTERNATIONAL STANDARD
kit edition
987-1 1-15
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION
ORGANISATION INTERNATIONALE DE NORMALISATION
MEXAYHAPOAHAR OPrAHMSA!+IR no CTAHAAPTMSAUMM
Information processing systems - Data
communication - Twisted pair multipoint
interconnections
S ystèmes de traitement de l'information - Communication de données - Interconnexions
multipoints par paire torsadée
Reference number
IS0 8482 : 1987 (E)
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Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of
national standards bodies (IS0 member bodies). The work of preparing International
Standards is normally carried out through IS0 technical committees. Each member
body interested in a subject for which a technical committee has been established has
the right ta be represented on that committee. International organizations, govern-
mental and non-governmental, in liaison with 60, also take part in the work.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the IS0 Council. They are approved in accordance with IS0 procedures requiring at
least 75 % approval by the member bodies voting.
International Standard IS0 8482 was prepared by Technical Committee ISO/TC 97,
1 __ --
Information processing systems.
Users should note that all International Standards undergo revision from time to time
and that any reference made herein to any other International Standard implies its
latest edition, unless otherwise stated.
O International Organization for Standardization, 1987 O
Printed in Switzerland
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IS0 84û2 : 1987 (E)
INTERNATIONAL STANDARD
Information processing systems - Data
communication - Twisted pair multipoint
interconnections
e
1.4 This International Standard does not specify special en-
Scope and field of application
1
vironmental conditions, such as galvanic isolation, electro-
magnetic interference (EMI), radio frequency interference
1 .I This International Standard specifies the physical
(RFI), and human safety. This may form the subject of a future
medium characteristics for
addendum.
- twisted pair multipoint interconnections in either 2-wire
1.5 This International Standard is primarily a component
or 4-wire network topology in order to provide for half
specification. It is not sufficiently specified for satisfactory
duplex or duplex data transmission capability, respectively;
interoperations in all possible configurations. It is the responsi-
- a binary and bidirectional signal transfer of the inter-
bility of implementors to ensure that their intended configura-
connected endpoint systems;
tion will allow satisfactory interoperation.
- the electrical and mechanical design of the endpoint
system branch cables and the commmon trunk cable, which
1.6 This International Standard may be combined with any
may be up to 500 m in length;
appropriate set of functional and additional environmental
characteristics so as to meet the practical data transmission
- the component measurements of the integrated circuit
requirements in the field of local or wide area networks.
type generators and receivers within the endpoint systems;
- the applicable data signalling rate up to 1 Mbit/s.
e 2 Reference
CClTT Recommendation V. 11, Electrical characteristics for
1.2 The defined electrical component characteristics and
balanced double-current interchange circuits for general use
measurements are in close conformance with the twisted pair
with integrated circuit equipment in the field of data corn-
point-to-point characteristics given in CClTT Recommendation
munica rions.
v.ll.
3 Definitions
1.3 This International Standard does not describe a complete
The definitions of the specified electrical characteristics are
physical interface and has no functional interface charac-
given in annex 5.
teristics, such as
- number of interchange data and control circuits;
4 Symbolic representation of an interchange
- type, size and pin allocation of the endpoint system
circuit (see figure 1)
branch cable connectors;
The symbolic representation of an interchange circuit is in prin-
- data and control signal encoding;
ciple as given in CClTT Recommendation V. 11.
- time relations between signals on the interchange
circuits; However, the generator of this International Standard includes
an additional control to place the device into the active state or
- mode of synchronous or asynchronous transmission;
the inactive, high impedance zero voltage state. This addition is
- signal quality for transmission and reception.
shown in the symbolic representation reproduced in figure 1.
1
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IS0 8482 : 1987 (E)
Balanced
Generator
I interconnecting cable 1 Receiver
'I I
I I
I I
I i
High
impedance
control
I I
Generator Receiver
interchange point interchange point
vab = Generator output voltage between points A and B
Vac = Generator voltage between points A and C
"bc = Generator voltage between points B and C
= Ground potential difference
vs
4 = Cable termination resistor
A, B and A', 8' = Interchange points
c, C' = Zero volt reference interchange points
(Signal ground)
NOTES
1 Two interchange points are shown. The output characteristics of the generator, excluding any interconnecting cable, are defined at the "generator
interchange point". The electrical characteristics to which the receiver must respond are defined without the cable termination resistor at the "receiver
interchange point".
2 Points C and C' may be interconnected and further connected to protective ground if required by national regulations,
Figure 1 - Symbolic representation of interchange circuit
5 Interconnection configurations (see figures 2 All balanced cables may be shielded if required by local regula-
tions. It may also be necessary to extend shielding across the
and 3)
branchltrunk cable connectors.
In general, the interconnection configuration consist of one
Depending on the type of multipoint operation, either a two
balanced trunk cable, which may be up to 500 m in length, and
wire or a four wire interconnection configuration may be used.
several balanced branch cables, each connecting an individual
Figure 2 shows a two wire multipoint configuration for half
endpoint system to the common trunk cable. The branch cable
duplex data transmission, while figure 3 shows a four wire
connection points may be spaced as appropriate. A branch
multipoint configuration for either half duplex or duplex data
cable may be up to 5 m in length.
transmission.
The balanced trunk cable shall be terminated by a termination
resistor at each end. At the individual endpoint system con- 6 Load on the multipoint medium
necting points, a branchkrunk cable connector shall be used.
This facilitates the generator/receiver load measurements Each endpoint system represents a load to the multipoint
defined in 6.1.2. The female connector(s) at each end of the
medium. The load consists of a passive generator andlor a
trunk cable shall accommodate the termination resistor(s). receiver with associated internal wiring and a balanced branch
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IS0 8482 : 1987 (E)
cable as shown in figures 2 and 3. In accordance with the multi- specifications in clauses 8 and 9 are selected such that an active
point half duplex data transmission principle, only one generator can drive the interconnecting trunk cable, terminated
at each end with not less than 120 n, and 32 so-called Unit
generator is in the active state at a given time.
Loads (ULs), representing the total load of all endpoint
Successful operation requires specification of the load in terms systems. The value of 1,0 UL is defined in 6.1.1.
of d.c. and a.c. loading. For d.c. loading, the component
Balanced two-wire trunk cable /-\
I\
--- +. _____------3_ * --------
+-A--- T--- 1)
I
I- ll I-
l
I I
Balanced two-wire
2)
1 ,A--, I I ,A&-,
Endpoint system Endpoint system Endpoint system
Figure 2 - Two-wire multipoint configuration
Balanced four-wire trunk cable
Rt Rt
Rt Rt
Endpoint system Endpoint system Endpoint system
Legend: 1 Signal ground 1, Protective ground
-
NOTES
1) Interconnection of the endpoint system signal ground is optional and depends on local regulations.
2) Branch cable shield is optional and, when provided, it connects to the endpoint system protective ground, which may be further connected to the
signal ground.
3) Trunk cable shield is optional and, when provided, it connects to a protective ground at one place. Interconnection of shield to branch cable
shields may be necessary.
Figure 3 - Four-wire multipoint configuration
3
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IS0 8482 : 1987 (E)
The voltage range takes into account the output and offset
6.1 Specification‘of d.c. loading
voltage of the generator, the common mode and internal
The d.c. loading specification limits the current of an active voltage of the receiver and the power supply voltage.
generator to a practical value. For this reason, a hypothetical
Unit Load (UL) is defined for a current/voltage measurement.
UL determination of the endpoint systems (see
6.1.2
figures 5 and 6)
6.1.1 UL definition (see figure 4)
When measuring the currentholtage characteristics at the
The value of 1,0 UL is defined by a current ranging between
male pin branchhrunk cable connector of one endpoint
-0,8 mA and + 1,0 mA when varying the voltage between
system, the measured generator shall be in the inactive state.
- 7 V and + 12 V. The correspondent currentholtage diagram
The measurement configuration is shown in figure 5.
is shown in figure 4.
Load of
endpoint
system
U
Figure 5 - Input currentholtage measurement
Figure4 - Current limit of 1,0 UL
+ 0.75 mA
= 0,75
+1,0 mA
-0,W mA
= 0,8
-0,8 mA
+ 1,2 mA
= 1.2
+ 1,0 mA
Ii
A’ +1,2 mA
I
-0,9 mA
= 1,125
-0,8 mA
Figure 6 - UL value determination
4
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IS0 8482 : 1987 (E)
The current/voltage measurement corresponds to that of the Table 1 - Receiver differential significant levels
V.ll receiver input in CClTT Recommendation V.ll, i.e. with
the voltage Via (or Vib) ranging between -7 V and + 12 V,
V, - VB, < -0,3 V
- VBr > +0,3 V
while Vit, (or Vi,> is held at zero volts, the resulting input current
Zia (or should remain within the shaded range shown in
Data circuits MARK, 1 SPACE, O
figure 4.
These measurements apply with the power supply of the
generator andlor receiver in both the power-on and power-off
conditions.
To determine UL from the measurements, the slope of the
8 Generator characteristics
bounds of the current limit of one UL, see figure 4, shall be
modified to the minimum slope required to fully contain the
The generator component is measured in the active, low im-
current/voltage characteristics, while the - 3 V and + 5 V
pedance state by the following tests using the measurement
intercept points are maintained. The actual value of UL is then
configurations shown in figures 7 to IO. The component may
equal to the larger of the two ratios of the actual current to the
be operated from a single-rail positive power supply.
one UL current at the - 7 V and + 12 V points (see the two ex-
amples of UL value determination in figure 6).
The tests are made for either binary state, whereby for the
0
magnitude of the voltage specifications both symbols I VI and
The slopes of the currents should be positive to lower the
I FI are used, respectively.
possibility of oscillations from negative resistance.
8.1 Open circuit voltage, Vo
When adding all measured UL values, the sum shall not exceed
32,O.
The voltage, when measured in accordance with figure 7, shall
be, between the
6.2 Specification of a.c. loading
- outputterminalsA,B: 1,5V G IVolorlV0l Q 6,OV
The a.c. loading on the interconnecting multipoint medium - terminals A,C and B,C: I VoalOrl voblorlvoalor
caused by the endpoint systems affects the transmission
1 vob I Q 6,o v
characteristics. This depends on application parameters, such
as type of balanced cable and data signalling rate. For this
reason, the following measurements are for guidance only and
8.2 Offset voltage, Vos
may have to be revised as necessary (see clause A.2 of
annex A).
The voltage, when measured in accordance with figure 8, shall
be, between the
6.2.1 Reflexion attenuation
-
load centre and terminal C : O V < Vos or vos Q 3,O V
The refiexion attenuation of an endpoint system should not be
- binary states, the difference:
1 Vos - vos 1 < 0,2 V
less than 20 dB. The measurement is made on the male pin
branch/trunk cable connector using a parallel test resistor of
120 Q. During measurement, the generator, if any, is in the in-
active state. 8.3 Terminated output voltage, Vt
The voltage, when measured in accordance with figure 9 by
6.2.2 Receiving distortion
varying the testing voltage Vin the range from -7 V to + 12 V
shall be, between the
The receiving signal distortion measured on the female pin
branch/trunk cable connector, terminated with a 120 0
1,5V < I V, /or1 vt I Q 5,O V
- output terminals A,B :
resistor, for mark/space reversals at the applied data signalling
- binary states, the difference:
1 V, 1 - I vt 1 < 0,2 V
rate shall not exceed 25 %.
NOTE - In the case of the twisted pair transmission medium, it is
assumed that the pattern dependent distortion is not very far outside
8.4 Rise time, tr, and imbalance voltage, Ve
the range of the mark/space reversals measurement.
When testing the mark/space reversais voltage Vss in accord-
ance with figure 10
7 Polarities and significant levels
-
the rise and fall time between 0,l and 0,9 of Vss on the
output terminals A,B shall be
The generator polarities and receiver significant levels corres-
pond to those in CClTT Recommendation V.ll. Table 1 is
V.ll.
reproduced from CClTT Recommendation
5
V'
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IS0 8482 : 1987 (E)
where 10.3 Generator current limitation (see figure 14)
tb = time of UI (unit interval); and The peak current in any lead to the generator shall not exceed
250 mA when testing in accordance with figure 14 by varying
the testing voltage Vin the range from - 7 V to + 12 V with a
V per ps.
slew rate of the voltage equal to or less than 1,2
- the resultant voltage due to imbalance between load
centre and terminal C shall be
This criterion should not be interpreted as a requirement that a
generator be capable of sourcing 250 mA. Rather, the sinking
V, a 0,4 V peak-to-peak.
generator shall not permit a composite current in excess of
250 mA, if multiple (sourcing) generators are providing that
current. (See annex A clause A.4 for additional information on
9 Receiver characteristics
generator contention.)
The receiver component is measured in accordance with the
measurement configurations shown in figures 11 and 12.
10.4 Transient over-voltage (see figure 15)
A component meeting these requirements results in a differen-
The measurement in accordance with figure 15 applies to both
tial receiver having a high input impedance, a small input
generators and receivers. Protection shall be provided from
threshold transition region between -0,3 V and +0,3 V dif-
transients that may occur on an interchange circuit when the
ferential, and allowance for an internal bias voltage not ex-
high current due to a single contending pair of generators is in-
ceeding 3 V in magnitude.
terrupted. (See annex A clause A.4 for additional information.)
9.1 Input sensitivity (see figure 11)
A passive generator or a receiver shall be able to withstand
without failure applied pulses of 15 ps duration at 1 % duty
The permitted range of input voltages VA. and VBt appearing at
cycle from a 25 V source having 100 B source impedance. Both
the receiver input terminals A and 6' measured with respect to
positive and negative pulses shall be applied between ter-
receiver terminal C' shall be between -7 V and + 12 V. For
minals A and C and between terminals B and C on passive
any combination of receiver input voltages within this permit-
generators and between terminals A and C' and between ter-
ted range, the receiver shall assume the intended binary state
minals B' and C' on receivers. If the component should
with an applied differential input voltage of k 0,3 V or more.
experience breakdown during the applied pulse, it shall return
In addition, the receiver shall not sustain any damage when
to the operational state within 200 ns after termination of the
connecting its input terminals A' or B' and C' to a testing
applied pulse.
voltage variable from - 10 V to + 15 V.
9.2 Input balance (see figure 12)
11 Environmental constraints
The balance of the receiver input voltage/current character-
istics and internal bias voltages shall be such that the receiver In order to operate a balanced interchange circuit at data
will remain in the intended binary state when a differential signalling rates up to 1 Mbit/s, the following conditions apply:
voltage VR3 of I0,6 V is applied through matched resistors
equal to 1 500 B to each input terminal, as shown in figure 12,
The total common-mode voltage at any point of the inter-
with the input voltages VR1 and VR2 ranging between -7 V
change circuit shall be within -7 V to +7 V. However, this
and + 12 V. When the polarity of vR3 reverses, the opposite
range is extended in the generator contention case to + 12 V
binary state shall be maintained under the same conditions.
(see clause A.4 of annex A.)
The common mode voltage at the receiver is the worst case
10 Fault condition tests
combination of
In order to ensure no damage occurs due to a single fault condi-
a) generator-receiver ground potential difference ( Ve, see
tion the components shall be tested in accordance with the
figure 1);
measurement configurations shown in figures 13 to 15.
b) longitudinally induced random noise voltage measured
between the receiver terminals A' or B' and C' with the
10.1 Generator short circuit (see figure 13)
generator ends of the cable A, 6, and C joined together;
A generator shall not sustain any damage as a result of short-
c) generator offset voltage Vos.
circuiting its output terminals A and 6 to each other.
10.2 Generator contention (see figure 14)
12 Component compatibility
A generator shall not sustain any damage as a result of con-
In certain instances, it may be possible to produce generators
necting its output terminals A or B and C to a testing voltage,
and receivers that meet the requirements of both CClTT
variable from - 10 V to + 15 V, under any output condition,
Recommendation V.ll and this International Standard.
binary O or 1, or passive.
6
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