Scaime eNod4-B - 4.4 Frames Structure

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User manual SCAIME: NU-soft-eNod4B-E-0716_236704-C.doc
Note: The frame error detection can be ignored. Value 0xFF of the CRC-8 always is admitted by eNod4 and a received
frame which is ended by such CRC-8 is considered as a frame without any error.
• Fast SCMBus checksum byte is obtained by summing all the frame previous bytes then setting b7 bit to 1.
4.4 Frames structure
4.4.1 Transmission organization
• frame : eNod4 address first
• byte : lsb first
• multi-bytes data : MSB first
4.4.2 Reading request
• request
Address
Command
CR
CRC
1 Hex byte
1 Hex byte (command)
1 ASCII byte (0D
H
)
1 Hex byte
• SCMBus response
Address
Status
Value
CR
CRC
1 Hex byte
2 Hex bytes
N ASCII Hex bytes
1 ASCII byte (0D
H
)
1 Hex byte
If the ‘decimal point position’ and the ‘unit’ settings are assigned to a non-null value, the response frame when
transmitting measurement contains the decimal point character (2E
H
) and the unit that is separated from the
measurement value by a space ASCII character (20
H
).
• Fast SCMBus response
STX
Status word
Value
Cks
ETX
02
H
2 Hex bytes
3 signed Hex bytes (2’s
complement)
Σ of previous bytes
and b7 bit set to 1
03
H
Note: Because values are encoded in signed hexadecimal bytes format (2’s complement) some data bytes can be
equal to STX (02
H
) or ETX (03
H
) or DLE (10
H
) so before those specific bytes values a DLE (10
H
) byte is inserted. The
eNod4 address is not transmitted in the frame.
4.4.3 Functional command request (tare, zero...)
• request :
Address
Command
CR
CRC
1 Hex byte
1 Hex byte (command)
1 ASCII byte (0D
H
)
1 Hex byte
• response (SCMBus and fast SCMBus) :
Address
Command
CR
CRC
1 Hex byte
1 Hex byte (command)
1 ASCII byte (0D
H
)
1 Hex byte
If the command execution is successful, eNod4 sends back the request frame that has been received as an
acknowledgement.
4.4.4 Error frame
In case of an error upon reception of a request, eNod4 sends back an error frame that contains an error code:
• response (SCMBus and fast SCMBus) :
Address
Error code
CR
CRC
1 Hex byte
1 Hex byte (command)
1 ASCII byte (0D
H
)
1 Hex byte
• The error codes are listed below: