36 D50 PLC User's Manual
Double Mode Address Designation
• Words are composed of two bytes put together. The designation for a word is exactly the
same as the designation for the byte, consisting of a one character register type and a 4 digit
word address. Bytes hold 8 bits of data, words hold 16 bits of data.
• The type of instruction used determines whether the register is processed as a single byte or a
word. For comparison instructions (>, <, ==, etc.), the programmer must be in “Double
Mode” to enter a word comparison (refer to program loader manual for details). For
application instructions, those instructions that start with a D in front of the related instruction
are word instructions, and process the data as 16-bit words instead of bytes.
Example 1:
Example 2: Comparison Instruction
Byte
Word
W0 is processed as 8 bit (1 byte) data (0 to
255).
S is processed as a value from 0 to 255.
Word W0 is processed as 16 bit (1 word) data
(0 to 65,535).
S can be a value from 0 to 65,535.
LET
D=W0
S=250
DLET
D=W0
S=2500
The example shows comparison instructions being used in the single mode
of GPC. The parameters W0005 and M0003 represent only 8 bits of data.
The high 8 bits are NOT used as part of the comparison.
In this example, GPC is in double mode and comparison instructions are
used. The comparison is performed on 16 bits of data. All of word W0005
and M0003 will be compared.
W0005
=<M0003
D W0005
=<M0003
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