II - DCE FEL ČVUT v Praze

Glossary
Substitute value
S7-300 backplane
bus
T
Terminating
resistance
Time-out
Transducer
Transmission rate
U
User data
Glossary-12
A value which is output to the process if a signal output module is faulty, or
which is used in the user program instead of a process value if a signal input
module is faulty. Substitute values can be defined by the user (e.g. ’hold last
value’).
A serial data bus which is used by the modules to communicate with one
another and which supplies them with the necessary voltage. The connections
between the modules are made with bus connectors.
A resistance for power matching on the bus cable; terminating resistances are
always required at the end of a cable or segment.
The terminating resistances of the ET 200 are connected and disconnected in
the bus connector.
If an expected event does not occur within a specified period of time, this
time is known as a “time-out.” In the HART protocol there are time-outs
for the response of a slave to a message from the master, and for the pause
after each transaction.
Sensor (measuring transducer) or actuator (signal control element). A
transducer can be implemented by a smart field device.
The transmission rate is the speed at which data are transmitted and indicates
the number of bits transmitted per second (transmission rate = bit rate).
Transmission rates of 9.6 Kbps to 12 Mbps are possible for the ET 200.
User data can be exchanged between a CPU and a signal module, a function
module, or a communications processor via process image or via direct
access. User data can be digital and analog input/output signals from signal
modules or control and status information from function modules.
I/O Modules with Intrinsically-Safe Signals
C79000-G7076-C152-04