![background image](http://html1.mh-extra.com/html/omron/c500-asc04/c500-asc04_operation-manual_743033149.webp)
Glossary
143
tion or format, or supplies a memory address where data can be stored. Similar
to a parameter and sometimes used interchangeably is the term “argument”.
Where a parameter usually supplies some type of control information to the
function or command, an argument is usually a variable that supplies needed
data.
PC program
A program that runs the PC; it is written in the Ladder Diagram programming lan-
guage.
polling
A process whereby the microprocessor periodically checks the value of a speci-
fied bit or byte, and depending on that value, the microprocessor takes some
specified action.
port buffer
Special memory that is used to temporarily store data that has just been re-
ceived or is about to be sent out through a communication port.
program counter
A microprocessor register that keeps track of program execution. It is used for
assembly language programming.
RAM
Stands for Random Access Memory and is used for running the ASCII Unit pro-
gram. RAM will not retain data when power is disconnected. Therefore data
should not be stored in RAM.
Read Flag
A PC hardware flag that indicates when data can be read from the PC. When this
flag is set, data can be accessed by a peripheral device.
reading/writing
When something is read, it is taken or copied from a remote location and brought
to the reference point. When something is written, it is sent from the reference
point to a remote or peripheral device.
RS-232C interface
The industry standard connector for serial communications. The ASCII Unit
communication ports use RS-232C connectors.
cycle time and refreshing
The PC is constantly scanning through its program, checking all of its inputs and
adjusting its outputs. The time required for the PC to run through its program one
time is called the cycle time. Each time the PC completes one cycle of its pro-
gram, it updates or refreshes its outputs. The ASCII Unit cannot read data from
the PC during data refresh.
stack pointer
A microprocessor index register used for assembly language programming.
start address
The starting address of a block of data. This term is used as a parameter in many
of the assembly language monitor mode commands.
start mode
Indicates how the ASCII Unit starts up when power is first applied or the Unit is
reset. The two choices are manual mode and automatic mode. The mode can be
selected by setting pins one and two of the left-side DIP switch.
START/STOP switch
A toggle switch on the front panel of the ASCII Unit used for starting and stopping
execution of the ASCII Unit program.
upload/download
Upload usually refers to the transfer of a program or information from a remote
device to a computer or other controlling device. Download usually refers to data
transfer from a computer or other controlling device to a remote device. From the
users point of view, if data is being sent to another device, it is being down-
loaded. If data is being received from another device, it is being uploaded.
valid signal line
A parameter of the OPEN command which specifies which communication sig-
nals (CTS, DSR, RTS) are to be used for handshaking.
Summary of Contents for C500-ASC04
Page 1: ...C500 ASC04 ASCII Unit Operation Manual Revised February 2001 ...
Page 5: ...iv ...
Page 7: ...vi ...