[KBA-78953] Communication issues between OSDP readers and some Mercury hardware - Synergis™ Softwire | Mercury

Synergis™ Softwire | Mercury

[KBA-78953] Communication issues between OSDP readers and some Mercury hardware

This article explains why you might not be able to establish communication between OSDP readers and some Mercury intelligent controllers or MR panels.


IMPORTANT: This is an important notice for users deploying Mercury hardware with Synergis™ Softwire. Communication between the following Mercury hardware and OSDP readers might not work:
  • Series 2 MR50 or MR52 panels
  • Series 3 MR50 or MR52 panels
  • MR51e or MR62e panels
  • EP1501, EP1502, or EP4502 intelligent controllers
  • LP1501, LP1502 or LP4502 intelligent controllers


In some installation environments, OSDP readers interpret non-driven 485-lines as data, which prevents the panel and the reader from communicating properly.


Depending on your Mercury hardware, you might need to add a 1k ohm resistor on your panel.
  • Starting with the hardware revisions listed in the table later in this section, the 1k ohm resistor is integrated in the panel. If you have the listed hardware and firmware versions or later, you do not need to add the resistor.
  • To fix the issue on panels that do not have the resistor integrated in the panel, you must add the 1k ohm resistor to pull down the Mercury DAT/DO to GND line. This process creates a communication bias which ensures that the reader interprets the data correctly.
    NOTE: There must be no ground faults in your installation. Make sure that the DC Ground (power supply return) is not connected to the earth ground.
Mercury hardware when the resistor was integrated
Panel or controller Assembly revision (white sticker) PCB revision (printed on back of PCB) Firmware version
Series 3 MR52 E B 3.21.1
Series 3 MR50 F F 3.21.1
LP4502 C B 1.27.1
LP1502 C C 1.27.1
LP1501 B B 1.27.1
  • If you replace your hardware (for example, replacing a Series 3 MR52 revision D with revision E), you do not have to remove the resistor that was added on the panel.
  • If you replace your hardware, no configuration is required in Synergis™ Softwire for the 1k ohm resistor. When you select an OSDP reader for the panel in Config Tool, the change for the resistor is handled by the Mercury firmware. If you select a different type of reader, the resistor is not enabled.

More information

For more information about this issue, contact Mercury Technical Support at TechSupport@Mercury-Security.com or Genetec™ Technical Support at https://gtap.genetec.com.