Glossary
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common data Data that is stored in memory in a PC and that is shared by other PCs in the same
system. Each PC has a specified section(s) of the area allocated to it. Each PC
writes to the section(s) allocated to it and reads the sections allocated to the oth-
er PCs with which it shares the common data.
constant An input for an operand in which the actual numeric value is specified. Constants
can be input for certain operands in place of memory area addresses. Some op-
erands must be input as constants.
control bit A bit in a memory area that is set either through the program or via a Program-
ming Device to achieve a specific purpose, e.g., a Restart Bit is turned ON and
OFF to restart a Unit.
control signal A signal sent from the PC to effect the operation of the controlled system.
Control System All of the hardware and software components used to control other devices. A
Control System includes the PC System, the PC programs, and all I/O devices
that are used to control or obtain feedback from the controlled system.
controlled system The devices that are being controlled by a PC System.
CPU See central processing unit.
CPU Bus Unit A special Unit used with CV-series PCs that mounts to the CPU bus. This con-
nection to the CPU bus enables special data links, data transfers, and process-
ing.
CPU Rack The main Rack in a building-block PC, the CPU Rack contains the CPU, a Power
Supply, and other Units. The CPU Rack, along with the Expansion CPU Rack,
provides both an I/O bus and a CPU bus.
C-series PC Any of the following PCs: C2000H, C1000H, C500, C200H, C40H, C28H, C20H,
C60K, C60P, C40K, C40P, C28K, C28P, C20K, C20P, C120, or C20.
CTS An acronym for clear-to-send, a signal used in communications between elec-
tronic devices to indicate that the receiver is ready to accept incoming data.
CV Support Software A programming package run on an IBM PC/AT or compatible to serve as a Pro-
gramming Device for CV-series PCs.
CV-mode A form of communications useable only with CV-series PCs. See C-mode.
CV-series PC Any of the following PCs: CV500, CV1000, CV2000, or CVM1
CVSS See CV Support Software.
cycle One unit of processing performed by the CPU, including SFC/ladder program
execution, peripheral servicing, I/O refreshing, etc. The cycle is called the scan
with C-series PCs.
cycle time The time required to complete one cycle of CPU processing.
data area An area in the PC’s memory that is designed to hold a specific type of data.
data length In communications, the number of bits that is to be treated as one unit in data
transmissions.
data link An automatic data transmission operation that allows PCs or Units within PC to
pass data back and forth via common data areas.
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