Siemens SIMOCODE pro Function Manual page 99

Access to memory areas
In SIMOCODE pro, only two memory areas are used, one each for addressing the bit
information and the register information.
The function codes for bit information (01, 02, 05, 15) thus always access the bit memory
area. The function codes for register information (03, 04, 06, 16, 23) always access the
register memory area.
The distinction as to whether information is read-only (r) or read/writeable (r/w), can be seen
from the dataset tables (see Section Modbus RTU data tables (Page 277)).
Figure 2-31
SIMOCODE pro - Communication
Function Manual, 11/2018, A5E40508495002A/RS-AC/003
Memory areas used in SIMOCODE pro
Communication
2.3 Modbus communication
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