Glossary
160
example, control codes can be used to position the cursor on a display or to
cause the printer to print a line of text as it is being typed.
DIP switches
There are two sets of DIP switches on the back panel of the ASCII Unit. Each
DIP switch has eight pins which can be set to either zero or one. These DIP
switches are used for setting hardware parameters such as the baud rate
and the start up mode.
EPROM/EEPROM
Nonvolatile memory (retains data when power is disconnected) is used for
permanent storage of up to three ASCII Unit programs. If the start mode is
set to automatic, the boot program will be loaded to the RAM from the
EPROM upon power up or reset. Programs can be read from and written to
the EPROM with the LOAD and SAVE commands, respectively.
execution sequence
The order of operation in which the PC and ASCII Unit hardware execute
their respective programs.
flag
A hardware flag is a bit that is set or cleared by the machine to indicate a
particular state or condition of the Unit to a peripheral device or to the pro-
gram. Examples of PC hardware flags are the Read and Write flags. A soft-
ware flag is set or cleared by the user to indicate to the hardware a particular
choice or option. For instance, software flags are sometimes used for setting
the direction of data transfer or the baud rate of a communication device.
hexadecimal
Hexadecimal or hex is a numerical system based on the number 16. One hex
digit can be represented by four binary digits in the range of zero to 15. The
numbers 10 through 15 are represented by the letters A through F, respec-
tively.
Index register
One of the microprocessor’s hardware registers. It is used for assembly lan-
guage programming.
interrupt number
A code that is sent from the interrupting device to the microprocessor indicat-
ing which device is “calling.” The interrupt number is especially important if
there is more than one peripheral device connected to a microprocessor.
interrupt
A signal sent to the microprocessor from a peripheral device that causes the
microprocessor to alter its normal processing routine. An interrupt says to the
microprocessor, “stop what you’re doing and pay attention to me !” When an
interrupt is acknowledged by the microprocessor, program execution will
branch to an interrupt service routine specifically written to handle the given
interrupt.
I/O device
I/O stands for input/output. Some examples of I/O devices are printers, mo-
dems, fax machines, and display terminals.
Machine No. switch
Used to select the unit number for the assignment of a data section. The Ma-
chine No. switch is located on the front panel of the ASCII Unit.
mantissa
The part of a numerical expression to the right of the decimal point.
memory area designator (@) A parameter of the PC READ and PC WRITE statements used to access
specific PC data areas. When using the memory area designator for data
transfer, the ASCII Unit does not need an accompanying PC data transfer
routine.
Summary of Contents for SYSMAC C200H-ASC02
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Page 7: ...TABLE OF CONTENTS viii Glossary 159 Index 163 Revision History 165 ...
Page 122: ...Appendix B Specifications 115 130 35 100 5 ...
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