Rockwell Automation RECOMM-485 RS485 DFI Communications Module - Manual (Page 59)

Glossary Glossary-1
G
LOSSARY
BCC (Block Check Character) - A technique for error detection in
data communications. A character is added to a transmission block,
which is compared with a second BCC computer by the receiver to
determine if the transmission is error free.
controller - Also called programmable logic controller. A solid-state
control system that has a user-programmable memory for storage
of instructions to implement specific functions such as I/O control,
logic, timing, counting, report generation, communication,
arithmetic, and data file manipulation. A controller consists of a
central processor, input/output interface, and memory.
See also
scanner.
CRC (Cyclic Redundancy Check) - A commonly used technique
for error detection in data communications. A polynomial algorithm
is performed on the data, and the resultant checksum is appended
at the end of the frame. The receiving device performs a similar
algorithm.
data rate - The speed at which data is transferred on the RS485
DF1 network. Each device on an RS485 DF1 network must be set
for the same data rate. You can set the RS485 DF1 module to 1200,
2400, 4800, 9600, 19.2 K or 38.4 kbps.
Datalink - A type of pointer used by some SP600 drives to transfer
data to and from the controller. Datalinks allow specified parameter
value(s) to be accessed or changed without using explicit
messages. When enabled, each Datalink consumes either four
bytes or eight bytes in both the input and output image table of the
controller. The drive determines the size of Datalinks.
DF1 - A Rockwell Automation Datalink layer protocol that combines
features of subcategories D1 (data transparency) and F1 (two-way
simultaneous transmission with embedded responses) of ANSI
x3.28 specification.
DPI (Drive Peripheral Interface) - A peripheral communication
interface used by various Reliance Electric drives and power
products.
DPI peripheral - A device that provides an interface between DPI
and a network or user. Peripheral devices are also referred to as
“modules” and “adapters.” The RS485 DF1 module and SP600 OIM
are examples of DPI peripherals.