The interface just goes hot while sending commands.
Yes - PLC-BUS interface is an eavesdropper!
Each PLC-BUS command on the bus can you receive with the PLC-BUS interface.
But ACK pulse, ID pulse or ON pulse are not a PLC-BUS command.
The ACK is just one PLC-BUS impulse on the bus.
The PLC-BUS interface generates a complete RS232 message from this one impulse!
When other PLC-BUS controller (e.g. mini controller) sends a command, you can receive this command with the PLC-BUS interface – it is like the bus echo, but the interface does not handle the ACK. So you do not receive an ACK message from PLC-BUS interface on the RS232 interface.
The ACK Pulse
The ACK Pulse is a single PLC-BUS Pulse that is generated in Position #3 of the PLC-BUS Frame immediately following the end of a PLC-BUS Message. Its purpose is to indicate to a transmitting device that the intended receiving device accepted the PLC-BUS Communication Packet. A PLC-BUS device only generates the ACK Pulse when it receives and accepts a PLC-BUS Communication Packet that has the ACK-bit set to 1.
The ID Pulse
The ID Pulse is a single PLC-BUS Pulse that is generated in Position #3 of the PLC-BUS Frame (immediately following the end of a PLC-BUS Message) that corresponds to the receiving device’s Unit ID. For instance, if the receiving device’s Unit ID is 4 then it will generate its ID Pulse 4 frames (AC half-cycles) after the end of the received PLC-BUS Message.