Sensor systems 2 AS-Interface

AS-Interface - Additional Information
12 Additional Information
12.1 Glossary
Address
Identifies a slave. On AS-Interface slaves, the factory
setting is 0. The address is automatically set to the required
value (between 1 and 31) in the system. It can
be changed at any time.
Actuator
A device which is externally controled and executes a
simple movement. For example: Magnetic switch,
valve. Sensor (antonym). One sometimes also sees
the word "actor", for instance in the AS-Interface brand
name.
Analogue module
A module for connecting analogue I/O signals, e.g.
voltage, current, temperature resistance detector. Data
transfer is obtained from Profile 7.3.
Coupling module
A device which, on the bus side, behaves like an AS-
Interface slave. On the other side it can supply power
to four binary actuators or sensors which are not buscompatible.
There is one sensor/actuator per message
bit.
APM
Alternating pulse modulation. Representation of the
bits on the AS-Interface cable. Each bit corresponds to
one sin² pulse. Each positive pulse is followed by a
negative pulse, and vice versa. Extremely resistant
against noise.
AS-Interface specification
According to Specification 2.04, a maximum of 31 binary
I/O modules can be connected. Specification
2.11 states that up to 62 binary modules can be connected.
These are denoted as A/B slaves. Profile 7.3
defined in Specification 2.11 permits the connection
and data transfer of up to 31 analogue modules.
Bit error rate (BER)
Specifies the average number of transmission errors.
Operational current
Current Ie, required by the device for correct operation.
The AS-Interface current consumption on modules is
calculated by adding together the operational current
and the output current Iout. Data integrity
In accordance with DIN 19244, a measure for data
transfer error protection. The lowest data integrity
class is I1, the highest is I3.
I/O configuration
For four-way I/O modules for example, specifies which
of the 4 data bits of the message are inputs and which
are outputs. Cannot be modified.
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Gateway
A master, which also manages the connection to a
higher-level bus. In this sense, it functions as a slave.
ID code
Identifies the slave type. The ID code is specified by
the slave manufacturer and cannot be modified.
Hamming distance (HD)
The HD specifies how many errors (e) a code can detect
depending on its error detection algorithm (HD = e
+ 1). The HD only relates to error detection in messages.
Usually, fieldbus HD = 4.
Configuration data
Image of an actual slave on AS-Interface
(= actual status of an AS-Interface network). The configuration
data (I/O, ID) is stored in the list of detected
slaves (LDS).
Master
Higher-level control unit on bus systems.
Master/slave access principle
A higher-level master polls the slaves in sequence (i.e.
in accordance with their addresses). Each slave addressed
responds with its data.
Parameter bits
These specify how the individual parameters of a
slave are set. For example, open/close, absolute/relative
distance in US sensors, bright/dark switching for
photoelectric sensors. They can be modified if required.
Parity check
Simple error check. On AS-Interface, the sum of the
user bits within a message (address, data, control bits,
parity bit) must be even. The parity bit is selected by
the transmitter.
Project data
Setpoint status of an AS-Interface network. The configuration
data of all slaves (I/O, ID) is stored in nonvolatile
memory in the master (list of projected slaves,
LPS).
By comparing the setpoint and actual configuration,
the master can detect slaves that have been connected
incorrectly or are missing.
Residual error probability
Specifies the average number of transmission errors
that remain once all error detection strategies have
been applied.
Subject to reasonable modifications due to technical advances. Copyright Pepperl+Fuchs, Printed in Germany
Pepperl+Fuchs Group Tel.: Germany +49 621 776-0 USA +1 330 4253555 Singapore +65 67799091 Internet http://www.pepperl-fuchs.com
Issue date 2004-11-19 - Catalogue AS-Interface 2004/2005