B&R Automation PC 620, User Manual

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Appendix A • Glossary
Appe
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A
563 Automation PC 620 with 945GME N270 CPU board User's Manual V 1.10
RAM
An abbreviation for " R andom A ccess M emory". Semiconductor memory which can be read or
written to by the microprocessor or other hardware components. Memory locations can be
accessed in any order. The various ROM memory types do allow random access, but they
cannot be written to. The term RAM refers to a more temporary memory that can be written to
as well as read.
Real time
A system is operating in real time or has real-time capability if the input sizes (e.g. signals, data)
are received and processed in a defined time period, and the results are made available in real
time for a partner system or the system environment. See also "real-time demands" and "real-
time system".
ROM
An abbreviation for " R ead- O nly M emory". Semiconductor memory where programs or data were
permanently stored during the production process.
RS232
R ecommended S tandard N umber 232 . Oldest and most widespread interface standard, also
called a V.24 interface. All signals are referenced to ground making this an unbalanced interface.
High level: -3 to -30 V, low level: +3 to +30 V; cable lengths up to 15 m, transfer rates up to 20
kbit/s; for point-to-point connections between 2 stations.
RS422
R ecommended S tandard N umber 422 . Interface standard, balanced operation, increased
immunity to disturbances. High level: 2 to -6 V, low level: +2 to +6 V; 4-wire connection
[inverted/not inverted], cable lengths up to 1200 m, transfer rates up to 10 Mbit/s, 1 sender can
carry out simplex communication with up to 10 receivers.
RS485
R ecommended S tandard N umber 485 . Interface standard upgraded from RS422. High level: 1.5
to -6 V, low level: +1.5 to +6 V; two-line connection [half-duplex mode] or four-line connection
[full-duplex mode]; permissible cable length up to 1200 m, transfer rates up to 10 Mbit/s. Up to
32 stations (sender/receiver) can be connected to an RS485 bus.
RTS
An abbreviation for " R equest T o S end". A signal used in serial data transfer for requesting send
permission. For example, it is sent from a computer to the modem connected to it. The RTS
signal is assigned to pin 4 according to the hardware specifications of the RS-232-C standard.
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