Rockwell Automation 20-COMM-S RS-485 DF1 Adapter - Manual (Page 54)

Glossary-4
Hold Last
When communications are disrupted (for example, a cable is
disconnected), the adapter and PowerFlex drive can respond by holding
last. Hold last results in the drive receiving the last data received via the
RS-485 DF1 connection before the disruption. If the drive was running
and using the Reference from the adapter, it will continue to run at the
same Reference.
I
I/O Data
I/O data, sometimes called “implicit messages” or “input/output,”
transmit time-critical data such as a Logic Command and Reference. The
terms “input” and “output” are defined from the scanner’s point of view.
Output is transmitted by the scanner and consumed by the adapter. Input
is transmitted by the adapter and consumed by the scanner.
L
Logic Command/Logic Status
The Logic Command is used to control the PowerFlex drive (e.g., start,
stop, direction). It consists of one 16-bit word of input to the adapter
from the network. The definitions of the bits in this word depend on the
drive.
The Logic Status is used to monitor the PowerFlex drive (for example,
operating state, motor direction). It consists of one 16-bit word of output
from the adapter to the network. The definitions of the bits in this word
depend on the drive.
N Node Address
A RS-485 DF1 network can have as many as 255 devices connected to it.
Each device on the network must have a unique node address from 0 and
254.
Non-Volatile Storage (NVS)
NVS is the permanent memory of a device. Devices such as the adapter
and drive store parameters and other information in NVS so that they are
not lost when the device loses power. NVS is sometimes called
“EEPROM.”
P
Programmable Controller Communications Command (PCCC)
PCCC is the protocol used by some controllers to communicate with
devices on a network. Some software products (i.e., DriveExplorer and
DriveTools 2000), also use PCCC to communicate.