Innovate Motorsports OT-1 - Manual (Page 16)

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As we can see from the diagram on the right, values are read from the
ECU one after another, in a loop. Since it takes the ECU a certain
amount of time to respond to each query, the longer the list of the
channels, the longer it takes to complete the loop. Obviously, the longer
to takes to complete the loop, the larger the time gap between each
read of an individual value.
Now let’s look at how Low Priority Values fit into this.
Instead of being read once each time through the loop, only one
Low Priority value is read each time through the loop. So, if you
have three low priority values, it will take three passes of the
loop to read them all once.
With our racetrack shaped diagram fresh in mind, let’s look at Low Priority inputs in practice. A
certain poorly maintained Suburban can provide three OT-1 channels that update at full MTS
rates. Even four channels is still very usable. For example, here is RPM, SPARKADV (ignition
timing), FUEL1_OL (Open Loop Status) and VSS (Vehicle Speed Sensor):
Read 1st
Value
Read 2nd
Value
Read 3rd
Value
Read last
Value
Repeat
Read 1st
Value
Read 2nd
Value
Read last
Value
Repeat
Read one Low
Priority Value
Low Priority
Value List