VMA1400 Series Overview and Engineering Guidelines Technical Bulletin 14
Zone Bus
The Zone Bus is a 2-wire communications bus that allows a computer
to commission and balance the VMA’s database. The computer must
have the proper software and must connect through the CablePRO
(AS-CBLPRO or IU-9100 in Europe) or CVTPRO (AS-
CVTPROx00-x) converter and the room sensor. The VMA also
supplies 15 VDC through the Zone Bus connector to power the
CablePRO or CVTPRO converter.
Note: The VMA supplies 15 VDC instead of 24 VAC supplied by
other Application Specific Controller (ASC) devices. The Zone Bus
does not function properly if connected to 24 VAC on the VMA.
Table 4: Zone Bus Specifications
Feature Specification
Type
Multi-drop serial communications bus, single ended
(North America) or differential (Europe)
Speed
1200 baud (bits per second)
Recommended Cable
Type
1.5 mm
2
(18 AWG) with or without shield
(Beldon 8760)
or
0.6 mm (24 AWG) without shield (unshielded
telephone cable)
Maximum Bus Length
Single Ended
150 meters (500 feet) with 1.5 mm
2
(18 AWG) cable
15 meters (50 feet) with 0.6 mm (24 AWG) cable
Differential
1500 meter (5000 feet) of 0.6 mm - 1.5 mm
2
(18-24 AWG) cable
Voltages
Single Ended
Logic High Voltage
Logic Low Voltage
4 VDC minimum (approximately)
1 VDC maximum (approximately)
Differential
Transmit
Receive
±5 VDC
±0.2 VDC
Data Transmission
1 Start Bit (low level)
8 Data Bits (least significant bit first)
1 Stop Bit (high level)
Isolation
Isolated from 24 VAC, BOs, and N2 Bus
Note: Do not share the Zone Bus common wire with any other
sensor or transmitter, as doing so can cause the VMA to misread the
sensor value, resulting in poor control.
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