Campbell CR23X, Руководство оператора

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A-1
APPENDIX A. GLOSSARY
ASCII: Abbreviation for American Standard
Code for Information Interchange (pronounced
"askee"). A specific binary code of 128
characters represented by 7 bit binary numbers.
ASYNCHRONOUS: The transmission of data
between a transmitting and a receiving device
occurs as a series of zeros and ones. For the
data to be "read" correctly, the receiving device
must begin reading at the proper point in the
series. In asynchronous communication, this
coordination is accomplished by having each
character surrounded by one or more start and
stop bits which designate the beginning and
ending points of the information (see
Synchronous).
BAUD RATE: The speed of transmission of
information across a serial interface, expressed
in units of bits per second. For example, 9600
baud refers to bits being transmitted (or
received) from one piece of equipment to
another at a rate of 9600 bits per second.
Thus, a 7 bit ASCII character plus parity bit plus
1 stop bit (total 9 bits) would be transmitted in
9/9600 sec. = .94 ms or about 1000
characters/sec. When communicating via a
serial interface, the baud rate settings of two
pieces of equipment must match each other.
DATA POINT: A data value which is sent to
Final Storage as the result of an Output
Instruction. Strings of data points output at the
same time make up Output Arrays.
EXECUTION INTERVAL: The time interval
between initiating each execution of a given
Program Table. If the Execution Interval is
evenly divisible into 24 hours (86,400 seconds),
the Execution Interval will be synchronized with
24 hour time, so that the table is executed at
midnight and every execution interval thereafter.
The table will be executed for the first time at
the first occurrence of the Execution Interval
after compilation. If the Execution Interval does
not divide evenly into 24 hours, execution will
start on the first even second after compilation.
See Section OV4.3.1 for information on the
choice of an Execution Interval.
EXECUTION TIME: The time required to
execute an instruction or group of instructions.
If the execution time of a Program Table
exceeds the table's Execution Interval, the
Program Table will be executed less frequently
than programmed (Section OV4.3.1 and 8.9).
FINAL STORAGE: That portion of memory
allocated for storing Output Arrays. Final
Storage may be viewed as a ring memory, with
the newest data being written over the oldest.
Data in Final Storage may be displayed using
the
7
Mode or sent to various peripherals
(Sections 2, 3, and OV4.1).
GARBAGE: The refuse of the data
communication world. When data are sent or
received incorrectly (and there are numerous
reasons this happens) a string of invalid,
meaningless characters (garbage) results. Two
common causes are: 1) a baud rate mismatch
and 2) synchronous data being sent to an
asynchronous device and vice versa.
HANDSHAKE, HANDSHAKING: The
exchange of predetermined information
between two devices to assure each that it is
connected to the other. When not used as a
clock line, the CLK/HS (pin 7) line in the CR23X
is primarily used to detect the presence or
absence of peripherals such as the Storage
Module.
HIGH RESOLUTION: A high resolution data
value has 5 significant digits and may range in
magnitude from +.00001 to +99999. A high
resolution data value requires 2 Final Storage
locations (4 bytes). All Input and Intermediate
Storage locations are high resolution. Output to
Final Storage defaults to low resolution; high
resolution output must be specified by
Instruction 78.
INDEXED INPUT LOCATION: An Input
location entered as an instruction parameter
may be indexed by keying "C" before it is
entered by keying "A"; two dashes (--) will
appear at the right of the display. Within a loop
(Instruction 87, Section 12), this will cause the
location to be incremented with each pass
through the loop. Indexing is also used with
Instruction 75 to cause an Input location, which
normally remains constant, to be incremented
with each repetition.