User`s manual

Watlow Controls Communications Guide 24
Data
The information that is transferred across
the communications bus. This may be a
setpoint, setup parameter, or any
character. This information is transferred
to an address or register.
DB-9
A standardized connector shaped like the
letter “D” when viewed on edge. This
connector has 9 contacts. It is utilized on
most IBM AT compatible PCs as the serial
port.
DB-15
A standardized connector shaped like the
letter “D” when viewed on edge. This
connector has 15 contacts. It is utilized
on most IBM AT compatible PCs as the
game/midi port.
DB-25
A standardized connector shaped like the
letter “D” when viewed on edge. This
connector has 25 contacts. It is utilized
on most IBM AT compatible PC’s as the
parallel port when the PC end contains
socket contacts. Can also be the serial port
when the PC end contains pin contact.
Decode
This is the reverse of encode. When a
piece of data has information embedded in
it, decode is to extract that information.
Ex. To extract an “A” from 01000001.
DeviceNet
A software protocol / hardware interface
based on CAN. A low cost communication
link that connects industrial devices over a
network. Uses twisted pair wires for the
power and bus. Nodes can be removed or
inserted on the bus without powering down
the network.
Double Word
Equivalent to two words or four bytes.
This equals 32 bits.
Duplex
The ability to send and receive data at the
same time. “To listen and talk at the same
time.”
EIA
See Electronic Industries Association
EIA-232
Electronic Industries Association
developed this standard hardware interface
to allow one device to talk to another
device in full duplex mode. This method
uses a differential voltage between one
wire and ground. Also called an unbalanced
system since the ground wire carries the
sum of current of all lines. First standard
to gain wide acceptance by manufacturers.
Transmission is limited to about 50 feet.
EIA-422
Electronic Industries Association
developed this standard hardware interface
to allow up to 10 devices to be on a bus at
one time. This method uses a differential
voltage between two wires. Also called a
balanced system since each wire carries the
same current values. This has the
advantage of being immune to outside
electrical disturbances.
EIA-423
Electronic Industries Association
developed this standard hardware interface
to allow one device to talk to another
device in full duplex mode. This method
uses a differential voltage between one
wire and ground. Also called an unbalanced
system since the ground wire carries the
sum of current of all lines. This standard is
compatible with EIA-232. The outputs
were beefed up to allow transmission up to
4000 ft.
EIA-485
Electronic Industries Association
developed this standard hardware interface
to allow up to 32 devices to be on a bus at
one time. This method uses a differential
voltage between two wires. Also called a
balanced system since each wire carries the
same current value. This has the advantage
of being immune to outside electrical
disturbances.
EIA/TIA -232, -422, -423 and -485
Data communications standards set by the
Electronic Industries Association and
Telecommunications Industry Association.