Modbus High Level Interface (HLI)
The VESDA ModBus High Level Interface (HLI) links your VESDAnet1 with PC software monitoring tools, Building Management Systems (BMSs) or Fire Alarm Control Panels (FACPs), otherwise known as`host’, that support the ModBus protocol.
There are two models available:
• ModBus HLI Type 1 (VHX-0400) which echoes each character received on the RS232 link back to the host together with reply message.
• ModBus HLI Type 2 (VHX-0410) which has the echoing function disabled.
One ModBus HLI is used to interface to a VESDAnet. Modbus HLI supports up to a maximum of 40 VESDA detectors on a VESDAnet.The Modbus HLI supports VESDAnet detector zone numbers between 1 to 200. The Modbus HLI divides up the address range into to 7 logical networks. For example the first 30 addresses are considered in network 1, addresses between 31 to 60 are in network 2 and so on.
Smoke and Alarm Levels
The Smoke Level is reported relative to the Fire Alarm threshold where the full scale is 20. For example, if the Fire Alarm threshold is 0.5 %obs/m, a level of 0.1%obs/m is reported as 4. In other words, the Actual Smoke level = (Reported smoke value * Fire1 Threshold) / 20.
All VESDAnet faults are mapped on one or more of the Modbus HLI faults which are listed below
• Head Fault • Head Fault (Battery and Mains)
• Head Fault (Scanner2 ), and
• Flow Fault
VESDAnet faults categorised as network faults are mapped onto all zones, whereas zone faults are mapped onto that particular zone.