COMM failed status of Fire Alarm 8000 series

["albertleng" <albertleng@xxxxxxxxx>]

Hi.

I'm working on a VB programming project (residing in PC) which needs to
receive data from a Fire Alarm 8000 series via RS232 and all the data
received need to be converted to MODBUS addresses.

The Fire Alarm 8000 series will not send anything to the RS232
connected to my VB programming unless there's an event like Technical
Alarm, fire in a zone, fault and reset. I manage to capture all these
different events and convert them to MODBUS protocol addresses
respectively.

One of our customer's requirements is that whenever the Fire Alarm 8000
series is disconnected from RS232 port of my PC, my VB program will be
able to capture it and set the relevant bit in MODBUS addresses. This
can't be done because as i wrote earlier, the fire alarm wont write
anything to the RS232 as long as nothing happens. So, disconnecting
Fire Alarm 8000 series from my PC is the same as "nothing happens".

Does someone have any idea which my VB program can know when the fire
alarm is disconnected from the RS232 port of the PC?

Thanks.

Albert