Johnson Controls SNE Series User Manual

Table 21: M-Bus protocol rules (bus topology)
Category Rules
General Two direct M-Bus connections to the USB port are supported.
Connection requires a USB-to-M-Bus adapter at the USB port
Either FC port supports M-Bus devices
No restrictions in topology, but bus topology is strongly recommended
Number of devices The MR003USB adapter supports up to 10 loads
The ACC-USBMBUS-0 adapter supports up to 100 loads
Length depends on cable resistance, capacitance, number of devices, position of
devices, and configured communication speed. Example scenarios to help with
calculation:
Baud rate
1
,
2
Maximum number
of unit loads
Maximum distance
between converter
and devices
Maximum distance
for entire bus
64 3,000 m (9,842 ft) 5,000 m (16,404 ft)
(2 mm x 1.0 mm
[18 AWG], shield
recommended,
resistance < 90
Ohms)
64 1,000 m (3,281 ft) 4,000 m (13,123 ft)
(2 mm x 1.0 mm
[18 AWG], shielded,
resistance < 90
Ohms)
250 350 m (1,148 ft) 4,000 m (13,123 ft)
(2 mm x 0.8 mm
[20 AWG], shielded,
resistance < 30
Ohms)
2400
250 350 m (1,148 ft) 4,000 m (13,123 ft)
(2 mm x 0.8 mm
[20 AWG], shielded,
resistance < 30
Ohms)
64 350 m (1,148 ft) 4,000 m (13,123 ft)
(2 mm x 0.8 mm
[20 AWG], shielded,
resistance < 30
Ohms)
9,600
250 350 m (1,148 ft) 1,000 m (3,281 ft)
(2 mm x 0.8 mm
[20 AWG], shielded,
resistance < 30
Ohms)
Line length and type
38,400 64 350 m (1,148 ft) 1,000 m (3,281 ft)
(2 mm x 0.8 mm
[20 AWG], shielded,
resistance < 30
Ohms)
Cable Twisted pair cable (shielding optional)
Termination No termination
1 Unit load is a defined standby current. A device is permitted a current drain of one unit load by default but may consume more if it
is shown at the device (as an integer) and in documentation.
SNE Installation Guide18

Johnson Controls SNE Series Specifications

General

Brand	Johnson Controls
Model	SNE Series
Category	Network Hardware
Language	English