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Glossary
accumulator register
The arithmetic hardware register of the microprocessor.
ASCII Unit program
The BASIC program that runs the ASCII Unit and communicates with the PC
program.
Backplane
A rack of hardware slots sharing a common bus line to which the CPU and all of
its I/O Units are connected.
base address
The first address of a block of memory or data. When a block of data is to be
transferred with one of the I/O commands, the base address must be specified.
baud rate
The speed at which data is transferred during I/O operations. The baud rate for
the two ports is set with the right-side DIP switch. The standard baud rates are
300, 1200, 2400, 4800, 9600, and 19,200.
binary
The number system that all computers are based on. A binary digit can have only
two values, zero and one. The octal and hexadecimal number systems are
based on binary digits.
bit
The smallest piece of information that can be represented on a computer. A bit
has the value of either zero or one. A bit is one binary digit.
boot program
The BASIC program that is automatically loaded into the ASCII Unit RAM upon
power up or reset.
byte
A group of eight bits that is regarded as one unit.
communications port
A connector through which external peripheral devices can communicate with a
host computer or microprocessor. The ASCII Unit has two communications
ports used to connect to a personal computer, printer, or other I/O devices.
data transfer routine
The PC requires a dedicated data transfer routine incorporated into its program
in order to communicate with the ASCII Unit. A data transfer routine is not neces-
sary when the memory area designator parameter is used with the PC READ
and PC WRITE statements.
data word
PC data is organized into units called words. Each word contains 16 bits and has
a unique address in the PC memory. When transferring a block of data between
the PC and the ASCII Unit, it is necessary to specify the address of the first data
word in the block as well as the number of data words to be transferred. Through-
out this manual the terms word and data word are used interchangeably.
device control codes
Keyboard strokes entered with the control key depressed that send control mes-
sages to peripheral devices such as a terminal display or a printer. For 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 per-
manent storage of up to three ASCII Unit programs. If the start mode is set to
Summary of Contents for C500-ASC04
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