TL;DR

The Mercury MP1502-GT is a cost-effective variant of the standard MP1502 controller, designed to support 4 single-reader doors using onboard I/O only. It shares identical hardware with the MP1502 but uses a specialized license file to enable 4-door functionality while disabling RS-485 downstream communication. This makes it ideal for price-sensitive deployments where downstream expansion is not required.

Core Differences: MP1502 vs. MP1502-GT

Hardware

The MP1502-GT uses identical hardware to the standard MP1502. The board layout remains the same with 2 reader ports, 4 relay outputs, 8 inputs, and 2 RS-485 ports. The GT variant is differentiated entirely through firmware and licensing.

Door Configuration

• MP1502 (Standard): Supports 2 doors with in/out reader configurations, plus downstream SIO expansion

• MP1502-GT: Supports 4 independent single-reader doors using onboard SIO only (no downstream expansion)

RS-485 Communication

The GT variant disables RS-485 downstream communication. This means you cannot connect downstream SIO boards or expansion devices. The RS-485 ports are physically present but functionally blocked by the GT license file.

Reader Configuration

OSDP reader address mapping remains unchanged from the standard MP1502. For In/Out or Alternate Reader configurations, addresses 0 and 2 are used for Reader Port 1, while addresses 1 and 3 are used for Reader Port 2. There is no hard-coding of reader OSDP addresses, inputs, or outputs—all mappings are configurable.

OSDP Secure Channel

OSDP Secure Channel is fully supported across all 4 readers on the GT variant.

Licensing & Firmware

• The GT functionality is enabled via a specialized license file on firmware version 2.6 or later

• Controllers can be converted between standard MP1502 and GT by loading the appropriate license file

• GT units will receive bug fixes from Mercury but likely not new features introduced in standard MP1502 firmware

Setting Up the MP1502-GT Controller

Prerequisites

• Mercury MP1502 hardware (new or existing unit)

• Firmware version 2.6 or later

• GT-specific license file from Mercury

Installation Steps

1. Verify Firmware Version: Ensure the controller is running firmware version 2.6 or later. If not, update the firmware before proceeding.

3. Configure Doors in Genea: The system will auto-detect the GT controller using SDK command 1853 (feature code). Configure up to 4 single-reader doors through the Genea platform.

4. Connect Readers: Wire your OSDP or Wiegand readers to the appropriate reader ports. Remember that each door uses a single reader (no in/out configurations in 4-door mode).

5. Test Operation: Verify real-time event reporting, access control decisions, and I/O behavior for all 4 doors.

Reverting to Standard MP1502

If you need to restore standard MP1502 functionality (2 doors with downstream expansion capability), load a traditional MP1502 license file onto the controller. Either license type can be loaded regardless of what is currently installed, but the license file must be requested from Mercury.

Feature Comparison Summary

Feature	MP1502 (Standard)	MP1502-GT
Doors Supported	2 (with in/out readers)	4 (single reader each)
Wiegand Support	Yes	Yes
OSDP Support	Yes (Secure Channel)	Yes (Secure Channel)
RS-485 Downstream	Yes	No
Downstream SIO Expansion	Yes	No
Reader Ports	2	2
Relay Outputs	4	4
Inputs	8	8

Important Notes

• Simultaneous Reader Access: When two users swipe on readers connected to the same reader port simultaneously, both requests are processed with minimal delay (approximately 0.5ms)—typically unnoticeable to users.

• No Hard-Coded Mappings: Reader OSDP addresses, inputs, and relay outputs are fully configurable—there are no fixed mappings between readers and specific relays.

• Auto-Detection: Genea automatically detects the GT controller variant using SDK command 1853 (feature code).

• Unsupported Configurations: Attempting to configure downstream SIOs or expansion devices on a GT controller will result in an error. The system will log these attempts for troubleshooting.

Known Issues & FAQs

FAQ 1 : Readers go offline after reset, resync, or panel reboot

Configuration
Readers are configured correctly, and swipes work as expected.

Issue
After a hardware reset, resync, or MP1502-GT panel reboot, some or all readers may go offline.

How to resolve

If all readers are offline:
→ Use “Refresh All Ports” on the Interface Panel page.

The controller must be online in order to refresh the ports.
If readers are offline on a specific port only:
→ Refresh the doors on that port.

FAQ 2 : Refresh Button Inconsistency

Configuration
Readers are configured correctly, and swipe functionality is working as expected.

Issue
When refreshing a port on a working setup, readers sometimes do not come online on the first attempt.

How to resolve

Try refreshing the port multiple times.
If that does not work, try Refresh All Ports.
If the issue still persists:
- Perform a hardware reset and resync.
- Then attempt the refresh again.

FAQ 3 : Incorrect Reader Configuration on the Same Port Affects All Readers

Configuration
On a specific reader port:

One reader is configured correctly.
Another reader is configured incorrectly.

Issue

Both readers fail to work as expected.
Behavior is inconsistent:
- The correctly configured reader often does not function properly.
- The incorrectly configured reader may remain online, and swipe may still work.

Additional observations

Once the incorrect reader configuration is corrected, the setup starts working as expected.
In some cases, both readers continuously toggle between online and offline until a port refresh is performed.

FAQ 4 : Different Secure Channel Settings on Readers Sharing the Same Port

Setup

Two readers are configured on Reader Port 1, with addresses 0 and 1.
Both readers are initially configured with Secure Channel = OFF.