Data Format; Command Frame Format; Fcs Calculation Example - Omron E5CN Manual

SECTION 4 SYSWAY (E5@J and E5@X Format) Communications Procedures

4.1 Data Format

■ Command Frame Format

@
@
Communications
unit number
Header code
Data code
Text
FCS
Terminator
● FCS Calculation Example
Start
character
@(40H)
FCS = 4 0H + 3 0 H + 3 0 H + 5 2 H + 5 8 H + 3 0 H + 3 1 H = 4 BH
The calculation result (4B hex) is converted to ASCII and written to the FCS bytes.
4 → 34H
B → 42H
The + symbols indicate XOR (exclusive OR) operations.
4-2
Communi-
Header
Data
cations
code
unit num-
code
ber
FCS calculation range
The @ character (ASCII H'40) indicates the start of block format.
A number within the range 0 to 99 can be set in BCD. No response will be returned to a
node with a number outside of this range.
This is a 2-character alphabetic code that indicates the command type.
Set "02" only when reading and writing alarm value 2. Otherwise, set "01."
This area contains read values, write values, or status data. The data depends on the
command.
This is the Frame Check Sequence.
The FCS (Frame Check Sequence) is calculated by taking the exclusive OR of all char-
acters from the @ character to the last text character and converting the result to ASCII
characters.
Indicates the end of the block format.
The terminator is composed of "*" and CR (Character Return = H'0D).
The FCS (Frame Check Sequence) is calculated by taking the exclusive
OR of all characters from the @ character to the last text character and
converting that 8-bit result into two ASCII characters.
Communication
unit number
0 (30H) 0 (30H) R (52H) X (58H)
FCS Termi-
Text
nator
* CR
Data code
Header
code
0 (30H) 1 (31H)
FCS
4 (34H) B (42H)