e
e
N
N
o
o
d
d
3
3
-
-
D
D
D
D
i
i
g
g
i
i
t
t
a
a
l
l
d
d
o
o
s
s
i
i
n
n
g
g
c
c
o
o
n
n
t
t
r
r
o
o
l
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r
r
e
Nod3-
D
: User’s instructions
165 752-A
9/23
The CAN interface is connected using the CANH, CANL and REF (not mandatory) connections on the 9-pin
connector.
4
COMMUNICATION :
e
Nod3-
D
can communicate using several protocols :
- ModBus RTU
- SCMBus standard format or fast format.
- CANopen
Switching from the SCMBus protocol to the ModBus-RTU protocol (and reciprocally) can be done
by software programmation.
1) send the corresponding command
2) send the ‘storage in EEPROM’ command
3) reset (hardware or software)the device
See example describing how to switch from ModBus-RTU to SCMBus protocol in the document
SCMBUS communication Ref 165 756 Appendix A.
Switching from SCMBus/ModBus-RTU protocol to CANopen protocol (and reciprocally) can be
done by setting or removing the appropriate jumper (cf. §3) then by making a reset
4.1 ModBus RTU :
See the descritption of the different communication frames in the document : ModBus-RTU
communication Ref. 165754
4.2 SCMBus :
See the descritption of the different communication frames in the document : SCMBus communication
Ref. 165756.
The SCMBus protocol has got similarities with ModBus-TU. It is based on the master/slave structure
however it allows to transmit measurements continuously without collision management on the line. This
operating mode is only available in transmitter functioning mode.
The measurements transmission frequency depends on the serial baud rate thus transmitting 100 meas/s
is impossible at less than 19200 bauds. For fast measurement transmissions, use the fast SCMBus
format with wich 1200 meas/s can be expected at 115200 bauds.
Other methods of transmitting information without any master request :
- transmitter mode : measurement transmission triggered by a digital input.
- whatever the functioning mode is, physical calibration procedure : automatic transmission when
a step in the process is complete.
4.2.1
Fast SCMBus format :
The fast SCMBus format is particularly useful for measurement acquisition at the highest rate, for
example in order to analyze dynamic phenomena. This format should only be used for point-to-point
opreation in full-duplex.
So as to optimize the speed, in addition to using the fast SCMBus format, it is preferable to configure
e
Nod3-
D
in ‘non-processing transmitter’. In his operating mode, filters are disabled, set points are not
managed and there is no polynomial linearization.
4.3 CANopen :
e
Nod3-
D
supports CANopen communication protocol and is compliant with ‘CiA Draft Standard V301’.
Refer to the decription note : CANopen communication Ref. 165758.
