New to M1 and confused by the data bus?
The M1 RS485 data bus provides fast and reliable communication to M1 peripherals. Proper wiring, termination, and device addressing are key. Common mistakes can lead to headaches, so it is important to get it right.
These tips will help...
KNOW YOUR DEVICE TYPES
The rule: Do not duplicate device addresses within the same device type.
What are the device types and how do you know which is which? Let's shine some light on this subject...
- TYPE 1: All Keypads, Access Modules (M1KAM), and Supervised Power Supplies
- TYPE 2: Hardwired and Wireless Input Expanders - M1XIN, M1XRFTWM, M1XRFEG, and M1XRF2H
- TYPE 3: Output Expanders - M1XOVR
- TYPE 5: Serial Expansion Expanders - M1XSP, M1XSLU, M1PCSPIM
Here are a couple examples:
- It IS acceptable to have a keypad and an M1XIN at the same address
- It IS NOT acceptable to have both a keypad and M1KAM at a the same address
- It IS NOT acceptable to have an M1XIN and an M1XRFTWM at the same address
2 IS THE MAGIC NUMBER
2 is an important number to keep in mind when working with the M1 data bus:
- There can be NO MORE THAN 2 RUNS connected directly to the M1 data bus. When counting runs be sure to include any connections to the screw terminal block, as well as any connections to the J1 and J2 quick connectors.
- There must be EXACTLY 2 TERMINATION POINTS on the M1 data bus. The device at the end of each run must be terminated using the termination jumper on the device. If only 1 run is connected to the M1 data bus, a jumper must be installed on JP3 on the main control to provide the second termination point.
NO STARS OR T'S PLEASE
For multiple devices on a single run, the devices must be wired in a daisy chain.
PREFER HOME RUN WIRING? NO PROBLEM WITH DATA BUS HUBS!
Data bus hubs are designed to accept home run wiring. They also make installation quicker, easier, and neater. We offer 2 styles of data bus hubs for different types of wire and different wiring scenarios.
- M1DBH: This hub is typically used in new construction. It is designed for use with CAT5/CAT6 wire and provides RJ45 ports for connecting devices. Devices connected to this hub do not have to be terminated, since termination occurs at the hub using a special RJ45 terminating plug that is included with the hub. This hub can be located remotely if needed.
- M1DBHR: This hub is typically used in retrofit installations. It is designed for use with 4 conductor wiring and provides screw terminals for connecting runs. This hub creates 4 separate managed data bus branches. Each branch can accept 2 runs and requires 2 termination points (there's that magic number again!). This hub must be installed very close to the M1 Control. It CANNOT be installed remotely.