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What serial communications ports are available on a PM800 series meter and when should each be used?

PM800 Series meters without the Ethernet Communications card (PM8ECC) and the remote display adaptor (PM8RDA) have only one communication port (Comm 1). When adding PM8ECC or remote display adapter, two additional comm ports are added to the meter. When this occurs, the user needs to know when and how each communication port can be used.

Product Line:
PM800, PM820, PM850, PM870

Serial/Ethernet Communication 
RS-485 Communication
There are three Serial Comm ports on a PM800 when PM8ECC and PM8RDA Modules are installed. A user may not know which comm port to use depending on the communications requirement. 

The following serial communications ports are available on a PM800 when there is a PM8ECC and PM8RDA installed:

1. The PM800 series meter base unit has one 2-wire RS-485 port (Comm 1). RS-485 Slave Port
2. The PM800 Remote Display Module has one 2 or 4-wire RS-485 port (Comm 2). RS-485 Slave Port
3. The PM800 Ethernet Communications Card (PM8ECC) one 2 or 4-wire RS-485 port (Comm 3). RS-485 Master Port

When should each port be used?

1. The base unit 2-wire RS-485 port can be used to communicate directly with a PM800 if you have a 2-wire RS-485 daisy chain.
2. If you have a PM800 with a Remote Display module and you need to connect the PM800 to a 2 or 4-wire RS-485 daisy chain, you can use this communications port on the Remote Display Adapter. 
3. If you have a PM800 with a PM8ECC and you intend to use the Ethernet Communication card as a gateway, you will need to connect the downstream RS-485 wiring to the port on the Ethernet Communication card. This port is configurable for 2-wire or 4-wire via dip switches.

Note: When the PM8ECC is added to a PM800 Meter with a remote display adapter (PM8RDA), the RS485 communication port 2 on the remote display adapter becomes disabled. Only two RS485 ports (Comm 1 and Comm 3) can be used simultaneously. COM 1 is a RS-485 Slave Port and COM 3 is a RS-485 Master port.
Additionally, when the remote display adapter is added to a PM800 Meter without the PM8ECC, Comm 1 and Comm 2 can be used simultaneously. Both ports will require a different RS485 address (Device ID). 

Basic Unit

Remote Display Module

Ethernet Communications Card (PM8ECC)

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