Mercury MR52 (Dual Door Module) Setup
1.0 Introduction
The Mercury MR52 is a dual door, dual reader module that connect to Mercury EP, LP or MP controllers via 2-wire RS-485. The module supports 2 card readers, including OSDP readers and it has 8 inputs and 6 relays.
Four of the inputs are reserved for door functionality (door contact and request-to-exit) for each door, and 2 of the relays are pre-configured as strike relays. The remaining inputs and outputs can be used for general purpose I/O control.
The MR52 Series 2 module is a green-colored PCB and the MR52 Series 3 is a red colored PCB. Both module types are compatible with each other and completely interchangeable.
Mercury MR52 Series 2 | Mercury MR52 Series 3 |
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2.0 Power Supply to the MR52
The MR52 accepts 12VDC to 24VDC for power. Locate the power source as close to the interface as possible. Make power connection with a minimum of 18AWG wires. The input voltage is filtered and regulated to 5VDC or 12VDC.

3.0 S1 DIP Switch Setting and Controller Addressing
- The MR52 has a DIP switch (S1) - this is used to set the address and baud rate of the module. Switches 1 to 5 are used to set the device's RS-485 address. Switch 6 and 7 select the communication baud rate (the default baud rate for SCP hardware is 38,400). All other configuration settings are set via host software.

- The System Processor Module, for example: an LP4502, is assigned SPM number 0 - You can see this if you enable Advanced View for the controller properties and look within the Miscellaneous section.
Note: The SPM address is separate from the RS-485 address of downstream modules added to TB2 or TB3.

- The first downstream device/module added to the RS-485 bus is addressed as 0 by default. So if the MR52 is the first device you should therefore set S1 to address 0.
- The MR52 module communicates to a Mercury SPM/controller via the RS-485 communication link (TB6 connector on the MR52). The interface allows for multi-drop communication on a bus of up to 4,000 feet (1,200 m). The RS-485 interface can be set for either 2-wire or 4-wire configuration via the J3 jumper. By default the J3 jumper is set to 2-wire.

4.0 Add the MR52 to Doors.NET
Note: To add an MR52 dual door module to Doors.NET you must already have an EP, LP or MP SPM (controller) added and online.
- In Doors.NET go to Setup >> Hardware Setup >> All.
- The hardware tree will be displayed.
- At the top of the hardware tree will be the SCP/MSC (Mercury) communication gateway. Beneath the gateway the controllers will be listed.
- Select the controller which has the MR52 connected and refer to the properties on the right.
- Ensure that the controller is showing as online.

- Expand the Mercury SPM on the hardware tree.

- You will see the TB2 entry if the controller only has 1 RS-485 port or TB2 and TB3 if there are 2 RS-485 ports.
- Select the port which the MR52 is connected to.

- Click the MR52 icon from the hardware select ribbon bar.

- The MR52 module will be added to the TB2/TB3 entry on the hardware tree.
- Select the MR52 on the hardware tree and the module's properties will be displayed on the right.
Note: By default, the first module added to the RS-485 port will be addressed as 0, by default. To edit the module's assigned address you will need to have Advanced View enabled.

- Ensure the address matches what is set on the S1 DIP switch (as explained in step 3.0).
- If the MR52 is addressed correctly and set to the correct baud rate it should almost immediately show as online.
- Open Live Events and you should see events being posted from the MR52 module indicating - further indicating that the module is online.
Note: By default, the baud rate for the module is 38,400 - this is set in the properties of TB2/TB3 and is applied to all downstream devices/modules which are added to the bus.
TB2/TB3 Communication Port Settings