2.6 Point Passing

2.6 Point Passing

In this lesson: you will be able to route values between controllers using the gateway's point-passing engine, including multi-source aggregation functions.

Why controllers need to share values

Standalone, each controller runs its own program. But real buildings need controllers to share values — an outside-air temperature read by one controller used by all of them, or a demand signal averaged across a floor. That is Point Passing, and the gateway does it for you.

How Point Passing works

Point Passing acts like a manager: it reads values that controllers publish through their WINDO blocks, and it writes values down into other controllers through their EMS block (the “receive from manager” block) or broadcasts to a whole group via a group broadcast, which the controllers receive through their RGRP block. So the flow is: source controller publishes via WINDO, the gateway routes it, destination controller receives it via EMS or RGRP.

To build a route, you pick a source (a published value from one controller) and a destination (an EMS or group input on one or more other controllers). Save it, and the gateway keeps that value flowing automatically at each poll.

Combining multiple sources

Point Passing can also combine multiple sources into one. Instead of one-to-one, you feed several source values through a function: MAX, MIN, AVG, SUM, OR, or AND. So “the highest zone-demand on the floor” is a MAX route; “average space temperature” is an AVG route; “any zone calling” is an OR route. That is a lot of coordination logic with no controller programming at all.

The either-or rule (on the exam)

Point Passing and the optional Logic Programs feature are either-or. When Logic Programs is not licensed, Point Passing is fully editable — it is your routing tool. When Logic Programs is licensed, Point Passing becomes read-only: routing moves into the Logic Programs wiresheet instead, which is more powerful. So if you open Point Passing on a site and it will not let you edit, that is not a bug — it means Logic Programs is licensed and you should be routing there.

Key points

• Point Passing reads published values via WINDO and writes them via EMS (per-controller) or group broadcast received via RGRP.
• A route flows a source's published value to a destination input automatically at each poll.
• Six aggregation functions combine multiple sources: MAX, MIN, AVG, SUM, OR, AND.
• Point Passing and Logic Programs are either-or.
• If Point Passing is read-only, Logic Programs is licensed and routing lives in its wiresheet.

Check your understanding

1. Which blocks does Point Passing use to read from and write to controllers?
2. Name the six aggregation functions for combining multiple sources.
3. You open Point Passing and it is read-only. What does that tell you?
4. You want the highest of several zones' demand passed to a plant controller. Which function?