Glossary

 

 

 

 

and ‘distributed’ over the system. Distributed control is a concept basic to PC

 

Systems.

DM area

A data area used to hold only word data. Words in the DM area cannot be

 

accessed bit by bit.

DM word

A word in the DM area.

downloading

The process of transferring a program or data from a higher-level or host com-

 

puter to a lower-level or slave computer. If a Programming Device is involved,

 

the Programming Device is considered the host computer.

EEPROM

Electrically erasable programmable read-only memory; a type of ROM in which

 

stored data can be erased and reprogrammed. This is accomplished using a

 

special control lead connected to the EEPROM chip and can be done without

 

having to remove the EEPROM chip from the device in which it is mounted.

electrical noise

Random variations of one or more electrical characteristics such as voltage, cur-

 

rent, and data, which might interfere with the normal operation of a device.

EPROM

Erasable programmable read-only memory; a type of ROM in which stored data

 

can be erased, by ultraviolet light or other means, and reprogrammed.

error code

A numeric code generated to indicate that an error exists, and something about

 

the nature of the error. Some error codes are generated by the system; others

 

are defined in the program by the operator.

Error Log Area

An area used to store records indicating the time and nature of errors that have

 

occurred in the system.

even parity

A communication setting that adjusts the number of ON bits so that it is always

 

even. See parity.

event processing

Processing that is performed in response to an event, e.g., an interrupt signal.

exclusive NOR

A logic operation whereby the result is true if both of the premises are true or both

 

of the premises are false. In ladder-diagram programming, the premises are

 

usually the ON/OFF states of bits, or the logical combination of such states,

 

called execution conditions.

exclusive OR

A logic operation whereby the result is true if one, and only one, of the premises

 

is true. In ladder-diagram programming the premises are usually the ON/OFF

 

states of bits, or the logical combination of such states, called execution condi-

 

tions.

execution condition

The ON or OFF status under which an instruction is executed. The execution

 

condition is determined by the logical combination of conditions on the same

 

instruction line and up to the instruction currently being executed.

execution cycle

The cycle used to execute all processes required by the CPU Unit, including pro-

 

gram execution, I/O refreshing, peripheral servicing, etc.

execution time

The time required for the CPU Unit to execute either an individual instruction or

 

an entire program.

extended counter

A counter created in a program by using two or more count instructions in suc-

 

cession. Such a counter is capable of counting higher than any of the standard

 

counters provided by the individual instructions.

extended timer

A timer created in a program by using two or more timers in succession. Such a

 

timer is capable of timing longer than any of the standard timers provided by the

 

individual instructions.

151

Page 159
Image 159
Omron CPM1A operation manual Eeprom, Eprom