Operation Manual 37107F
MFR 3 - Multi Function Relay
Page 152/165
© Woodward
CAN Bus Structure
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CAN Bus
Transmission Telegram
The data in the following table can be processed using a Gateway GW 4 or a PLC and transmitted to other com-
munication busses. The MFR 3 sends its data via cyclic CAN messages with this.
The transfer rate of this communication is 125 kBaud.
The CAN ID, on which the MFR 3 is sending, is calculated as follows:
CAN ID = d‘800 + item number
(or H‘320 + ID/generator number)
(The ID number is a parameter, which can be set at the MFR 3, which influences the CAN ID directly on which
the item sends its visualization messages.)
A visualization message, which is sent by an MFR 3, consists of 8 bytes and is assembled as follows:
Byte 0
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
H‘DD
MUX number
data word 1
high byte
data word 1
high byte
data word 2
high byte
data word 2
high byte
data word 3
high byte
data word 3
high byte
In a visualization message the byte 0 is always used to show the hexadecimal value DD. This one defines the
message as a visualization message. Since the complete transmission telegram of the MFR 3 includes more than
three data words, byte 1 sends an additional MUX number starting with 0 in addition. Therefore it is theoretically
possible to send (256 × 3 = 768) words via the CAN ID. The whole telegram is built up as follows:
Line 1: MUX number 0, data word 1
Line 2: MUX number 0, data word 2
Line 3: MUX number 0, data word 3
Line 4: MUX number 1, data word 1
Line 5: MUX number 1, data word 2
Line 6: MUX number 1, data word 3
.
.
Line (n):
MUX number (n-1/3), data word 1
Line (n+1):
MUX number (n-1/2), data word 2
Line (n+2):
MUX number (n-1/1), data word 3
n depends on the total length of the item-specific telegram and cannot be larger than H’FF.
Current Direction Message
The current direction can be recognized via the prefix of the power. A positive transmitted value indicates ex-
ported power (power supplied to the mains, supply) and a negative transmitted value indicates imported power
(power supplied by the mains, consumption).
