Siemens SIMATIC S7 System Manual page 79

Figure 4-4 Accessing the accumulators
SM (special memory)
The SM bits provide a means for communicating information between the CPU and your
user program. You can use these bits to select and control some of the special functions of
the CPU, such as: a bit that turns on for the first scan cycle, a bit that toggles at a fixed rate,
or a bit that shows the status of math or operational instructions. You can access the SM bits
as bits, bytes, words, or double words:
Table 4- 12
Bit:
Byte, Word, or Double Word:
For more information, see the descriptions of the SM bits (Page 799).
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
Absolute addressing of SM memory
[byte address].[bit address]
SM
[size][starting byte address]
SM
PLC concepts
4.2 Accessing data
SM0.1
SMB86,
SMW300,
SMD1000
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