HGM-MZ to N2 Communications Adapter
Rev 1 (P/N 3015-5514)
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10. Operating Limitations When Using MZ-RD Remote Display
When an MZ-RD remote display is used, the N2 network will have access to the HGM-MZ as long as the MZ-
RD is in either the SYSTEM or ZONE VIEW screen. If the MZ-RD is set to display any other screen, it will
respond to polls from the N2 adapter with an HGM BUSY exception code. The N2 adapter will handle the
exception by marking most points as Unavailable and setting the Unavailable Reason point = HGM Busy.
When the MZ-RD is returned to the SYSTEM or ZONE VIEW screen, normal N2 monitoring will resume.
If the operator leaves the MZ-RD in some screen other than SYSTEM or ZONE VIEW for an extended period
of time (10 minutes default), the MZ-RD times out and automatically returns to either the SYSTEM or ZONE
VIEW screen. This will restore normal N2 monitoring.
11. Miscellaneous Notes
RS-485 communications wires ARE polarity sensitive. If the adapter does not communicate on the N2 RS-485
port, try swapping the communications wires on the N+ and N- terminal block screws. The HGM port uses the
same labels as the HGM main board, so if you match the wires to the labels, polarity should not be an issue
there.
If the adapter seems to not be functioning correctly, it can be restarted without restarting the HGM simply by
pressing the CPU RST button just below the “A” DIP switch. If you restart the adapter by cycling the HGM’s
power, you will have to wait for the HGM’s 15-minute warm-up cycle to end before PPM readings are
available! If restarting the adapter alone doesn’t help, try cycling power to the entire HGM.
When the adapter software first starts, it attempts to establish communications with the HGM before attempting
to communicate on the N2 port. Do not be concerned after cycling power or pressing CPU RST that no N2
activity is shown on the LEDs immediately. The software delays about 20 seconds after a restart before
attempting to establish N2 communications.
The LEDs are driven by adapter software states, not by the RS-485 hardware. If an RS-485 connection stops
working in the middle of receiving a message, the RX LED may stay on indefinitely until the connection starts
working again.
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