R S 2 3 2 C PO RT CONTRO L
ASC I I Codes
A
byte of computer data can be used in many ways. One of the
most common ways is to equate each combination of O's and I 's to
a particular letter of the alphabet or a symbol.
ASCII
is a widely
used scheme for doing this. Only seven of the eight bits in each
byte are used in
ASCII,
giving 1 28 possible combinations of bits.
Each combination is assigned to represent one of 52 letters (upper
and lower case), 10 numerals, 34 symbols or 32 'unprintable'
characters. The unprintable characters are used to represent such
things as carriage returns, backspaces and form feeds in a block
of text.
The
CVI
communicates
exclusively
in
ASCII
codes. Every byte
received or transmitted by the
CVI
must be interpreted as an
ASCII
character.
The table of
ASCII
characters is given at the end of this
section.
Binary data
A
byte of data will often represent a number which is stored in
the computer. This is done by using the 'binary' scheme. The
eight bits are weighted in importance or
significance
from left to
right. The right-most bit is the
least significant bit
(LSB),
and has
a weighting of 1. The next bit has a weighting of 2, the next has
4, the next
8,
and so on. The left-most bit in a byte is the
most
significant bit
(MSB),
and has a weighting of 1 28. To obtain the
decimal value of a binary number, simply add the weightings of
the bits which are a ' I '.
For example, take the binary number 0 1 000 1 1 1 :.
1 1 00 1 00 1 (binary)
=
l x l 28
+
l x64
+
Ox32
+
Ox l 6
+
I
x
8
+
Ox4
+
Ox2
+
I x l
=
1 28
+
64
+
8
+
1
=
20 1 (decimal)
Using this method, binary notation can represent the decimal
numbers from 0 (binary 00000000) to 255 (binary 1 1 1 1 1 1 1 1 ).
-
SOFTWARE UPDATE
Summary of Contents for CVI
Page 1: ...r e User Manual Computer Video Instrument...
Page 4: ...Startea 2 Video Melius...
Page 102: ...33 Quad mirror Slow scan across L J _J...
Page 103: ......
Page 104: ...56 Under over stencil 57 Under over catch up 58 Push to freeze...
Page 105: ...60 L J _JI L...
Page 106: ...80 Under over texture wipe L J _J...
Page 107: ...L J _Jd r...
Page 197: ...RS232C Port ControI 1 Rev 7 Software Update 1...
Page 268: ...Glossary 1 Index 5...
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