Specifications

CPU Memory: Data Types and Addressing Modes
5-9
S7-200 Programmable Controller System Manual
C79000-G7076-C233-01
Addressing the Analog Inputs (AI)
The S7-200 converts a real-world, analog value (such as temperature or voltage)
into a word-length (16-bit) digital value. You access these values by the area
identifier (AI), size of the data (W), and the starting byte address. Since analog
inputs are words and always start on even-number bytes (such as 0, 2, or 4), you
access them with even-number byte addresses (such as AIW0, AIW2, or AIW4),
as shown in Figure 5-5. Analog input values are read-only values.
Format: AIW [starting byte address] AIW4
AI W 8
Area identifier (analog input)
Access to a word-size value
Byte address
AIW8
byte 8 byte 9
15 8
MSB
7
0
LSB
Least significant byteMost significant byte
Figure 5-5 Accessing an Analog Input
Addressing the Analog Outputs (AQ)
The S7-200 converts a word-length (16-bit) digital value into a current or voltage,
proportional to the digital value (such as for a current or voltage). You write these
values by the area identifier (AQ), size of the data (W), and the starting byte
address. Since analog outputs are words and always start on even-number bytes
(such as 0, 2, or 4), you write them with even-number byte addresses (such as
AQW0, AQW2, or AQW4), as shown in Figure 5-6. Analog output values are
write-only values.
Format: AQW [starting byte address] AQW4
AQ W 10
Area identifier (analog output)
Access to a word-size value
Byte address
AQW10
byte 10 byte 11
15 8
MSB
70
LSB
Least significant byteMost significant byte
Figure 5-6 Accessing an Analog Output