only the structured text demo is available at the moment.

SDO Read / Write FBs are described in chapter 8.1.3 of the manual.

note:
S7 1200 supports maximum 4 (manual 8) parallel runnning SDO commands.

reading of the process image input data:
chapter 8.1.1
this chapter describes how use RDREC to read the process image input of the CM module

writing of the process image output data:
chapter 8.1.2
this chapter describes how use WRREC to write data to the process image output of the CM module.

Get Node & Network Status:
chapter 8.1.4
this chapter describes how use RDREC to read the diagnostic information Node & Network Status
this function should be implemented because it provides an overview of the status of the CM module and the status of the network especially of the slaves.
it is very helpful because
- process image data are only exchanged between the CM module and the network if the CM module and and at least one slave is operational
- it also provides error information

hint for SDO Read / Write, Get Process data In, Set Process Data Out, Get Node & Network Status:
REQ input:
REQ must be set to TRUE only for starting the function.
REQ must be FALSE for the subesequent calls when the function is running.

data format:
the data format of the received / transmitted data is little endian: LSB first
example:
16 bit value 16#0102 shall be written by a byte array "DB_Test".ByteData[0 - 1]
-> "DB_Test".ByteData[0] := 16#04 // bits 0 - 7
"DB_Test".ByteData[1] := 16#03 // bits 8 - 15

32 bit value 16#01020304 shall be written by a byte array "DB_Test".ByteData[0 - 3]
-> "DB_Test".ByteData[0] := 16#04 // bits 0 - 7
"DB_Test".ByteData[1] := 16#03 // bits 8 - 15
"DB_Test".ByteData[2] := 16#02 // bits 16 - 23
"DB_Test".ByteData[3] := 16#01 // bits 24 - 31

16 bit value has been received by a byte array "DB_Test".ByteData[0 - 1]
-> "DB_Test".ByteData[0] := 16#78 // bits 0 - 7
"DB_Test".ByteData[1] := 16#56 // bits 8 - 15
received value (PLC format): 16#5678

32 bit value has been received by a byte array "DB_Test".ByteData[0 - 3]
-> "DB_Test".ByteData[0] := 16#78 // bits 0 - 7
"DB_Test".ByteData[1] := 16#56 // bits 8 - 15
"DB_Test".ByteData[2] := 16#34 // bits 16 - 23
"DB_Test".ByteData[3] := 16#12 // bits 24 - 31
received value (PLC format): 16#12345678

location of data in the process image:
process image input:
the process image input is received by a byte stream: e.g.: "DB_Test".ByteData[] : array of byte
the location of a data object in the received byte stream depends of the CANopen configuration:
see <Process Image> of the CANopen Configuration Studio: Direction: IN -> column "Address" and column (Size (bit)"
Address of data object <-> "DB_Test".ByteData[Address of data object]
the data object covers the data bytes:
size: 8 bits "DB_Test".ByteData[Address of data object]
size: 16 bits "DB_Test".ByteData[Address of data object], "DB_Test".ByteData[Address of data object + 1] note: data format: little endian
size: 32 bits "DB_Test".ByteData[Address of data object], ... , "DB_Test".ByteData[Address of data object + 3] note: data format: little endian

process image data will be always read from Address 0:
- read data: Address 0, 1, 2, ...
- note: unused data bytes are also copied
the size of the process image input to be read is:
the greatest Address of a data object of Direction IN + the byte size of this data object

process image output:
the process image output is transferred by a byte stream: e.g.: "DB_Test".ByteData[] : array of byte
the location of a data object in the transmitted byte stream depends of the CANopen configuration:
see <Process Image> of the CANopen Configuration Studio: Direction: OUT -> column "Address" and column (Size (bit)"
Address of data object <-> "DB_Test".ByteData[Address of data object]
the data object covers the data bytes:
size: 8 bits "DB_Test".ByteData[Address of data object]
size: 16 bits "DB_Test".ByteData[Address of data object], "DB_Test".ByteData[Address of data object + 1] note: data format: little endian
size: 32 bits "DB_Test".ByteData[Address of data object], ... , "DB_Test".ByteData[Address of data object + 3] note: data format: little endian

write process image data starts with Address 0:
- written data: Address 0, 1, 2, ...
- note: unused data bytes must not be updated but they must be transferred
the size of the process image output to be written is:
the greatest Address of a data object of Direction OUT + the byte size of this data object"

_________________________________________________________________________