ALLEN BRADLEY 1747-L551 PLC Processor

GL–2
Glossary
DH-485 Network — The DH-485 network is a collection of devices
connected to the communication cable allowing information
exchange. A communication network based on the EIA Standard for
RS-485 using an Allen-Bradley proprietary protocol.
Discrete Input and Output (DIO) — The discrete input and output
is the transfer of one to 32 words between a SLC-500 processor and
a scanner. All 32 words of input data and all 32 words of output data
are updated on each SLC program scan.
DTE Controlled Answer — Type of modem that is unattended and
is attached directly to the phone lines. The interface module or the
SLC 5/03 processor acts as the Data Terminal Equipment (DTE)
which controls the modem via the DTR and RTS signals. The
module incorporates timeouts and tests to properly operate these
types of modems.
DTR Dialing (SLC 5/03 only) — Type of modem that lets you dial
a number or end a call based on the status of the RS232 DTR (Data
Terminal Ready) signal. To program the modem initialization string
and phone number into the internal memory of the modem, use a
dumb terminal (or PC running terminal emulation software like
Procomm, Window’s Terminal, or PBASE). Once you have
programmed the modem, activate the DTR signal to dial the number,
or deactivate the DTR signal to end the call.
Ethernet Network — A local area network with a baseband
communication rate of 10M bits per second.
EEPROM — Electrically Erasable Programmable Read Only
Memory module used to store, back-up, or transfer SLC 500
programs. The SLC 500 can read and write to an EEPROM.
Flash EPROM — Flash Erasable Programmable Read Only
Memory module. It combines the programming versatility of
EEPROMs with the security precautions of UVPROMs. This means
that you have the option of leaving your EPROM programs write
protected or unprotected.
Full-duplex — A high-performance protocol that allows
simultaneous two-way data transmission. For point-to-point
applications only.
Half-duplex — A high-performance protocol that can be used in
point-to-point and multi-point applications.
Publication 1747-6.2