1.4 Explanation of Constants
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1.4.2 Hexadecimal Constants (H)
Function of hexadecimal constants (H)
Hexadecimal constants are values which have been converted from binary into
hexadecimal. When entering and reading a hexadecimal constant, specify the value by
entering an H at the beginning.
Hexadecimal constants are primarily used to specify an ordering of 1’s and 0’s in 16−bit
data, such as system register settings and specification of control data for high −level
instructions. Hexadecimal constants are also used to specify BCD data.
In the PLC, the hexadecimal constant (H) is processed as binary (BIN) data in units of
16 bits, as shown below.
Example: Hexadecimal number “2A” (H2A)
Binary data
··· ·
Hexadecimal
Bit position
· · · · ·
0
0000
0
000000 0
A
1010
15 1211 8 7 4 3 0
2
1
Data is normally handled in units of one word (16 bits), however, it is also occasionally
handled in units of two words (32 bits).
The available range of a hexadecimal constant is:
16-bit equivalent data: H0 to HFFFF
32-bit equivalent data: H0 to HFFFFFFFF
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