PLC concepts
4.2 Accessing data
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
75
The following table shows the range of integer values that can be represented by the
different sizes of data.
Table 4- 3
Decimal and hexadecimal ranges for the different sizes of data
Representation Byte (B)
Word (W)
Double Word (D)
Unsigned Inte-
ger
0 to 255
16#00 to 16#FF
0 to 65,535
16#0000 to 16#FFFF
0 to 4,294,967,295
16#00000000 to 16#FFFFFFFF
Signed Integer
-128 to +127
16#80 to 16#7F
-32,768 to +32,767
16#8000 to 16#7FFF
-2,147,483,648 to +2,147,483,647
16#8000 0000 to 16#7FFF FFFF
Real (IEEE 32-
bit Floating
Point)
Not applicable
Not applicable
+1.175495E-38 to +3.38 (positive)
-1.175495E-38 to -3.38 (negative)
Data in other memory areas (such as T, C, HC, and the accumulators) are accessed by
using an address format that includes an area identifier and a device number.
4.2.1
Accessing memory areas
I (process-image input)
The CPU samples the physical input points at the beginning of each scan cycle and writes
these values to the process image input register. You can access the process image input
register in bits, bytes, words, or double words:
Table 4- 4
Absolute addressing for I memory
Bit:
I
[byte address].[bit address]
I0.1
Byte, Word, or Double Word:
I
[size][starting byte address]
IB4,
IW7,
ID20
Q (process-image output)
At the end of the scan cycle, the CPU copies the values stored in the process image output
register to the physical output points. You can access the process image output register in
bits, bytes, words, or double words:
Table 4- 5
Absolute addressing for Q memory
Bit:
Q
[byte address].[bit address]
Q1.1
Byte, Word, or Double Word:
Q
[size][starting byte address]
QB5, QW14,
QD28
