Communication Formats: I/O Modules

The module returns general fault and input data along with the value of the system clock (from its local chassis) when the data changes. The system clock resides in the module, and is synchronized with all of the other system clocks in the same chassis (when there is a CST master in the chassis).

The timestamp samples the system clock after the data has been sampled and all filter delays are completed.If Change of State is enabled for any input points, the timestamp reflects the time when the module detected the change of state.

If the module detects more than one change of state before it manages to send the data out (either because there are several input points with the change of state enabled, or because the one point is changing rapidly), the timestamp is written into the buffer each time the module detects a change of state. Thus, the timestamp reported to the controller reflects the last enabled change of state that occurred before the data was transmitted.

The most effective way to use the CST system to coordinate outputs with inputs is to use output and input modules residing in the same chassis and synchronized with the same CST master. This makes it possible to schedule an output change of state up to 16 seconds after an input change of state, simply by doing arithmetic on the low order bits of the CST timestamps. The CST feature then performs the synchronization of outputs with inputs for you with a high degree of precision.

Another controller owns this module. This controller does not write configuration and can only listen to the module as long as there is an owner controller actively controlling it.

The module returns only general fault and input data.

The owner controller sends the module only output data.

The output sent to the module has an additional schedule time (in CST time format). The output transition occurs when the module’s CST time matches the schedule time.

The CST clock resides in the module and is synchronized with all the other clocks in the same chassis when there is a CST master in the chassis.

Input timestamping can be used in conjunction with the scheduled outputs feature so that, after input data changes state and a timestamp occurs, a synchronized output will actuate at some computed time in the future. You must allow a long enough delay so the timestamp gets input from the input module at its RPI, the control program computes the new output at its scan rate, and the output module gets its new data at its RPI. Generally, this will be several milliseconds.

The module keeps only one schedule time and overwrites it every time the controller sends new output. If you change the schedule time before the previously scheduled event, the previous event never happens. When the scheduled time occurs all outputs in the module switch to their new values. Before the scheduled time occurs, no outputs in the module change their states.

The most effective way to use the CST system to coordinate outputs with inputs is to use output and input modules residing in the same chassis and synchronized with the same CST master. This makes it possible to schedule an output change of state up to 16 seconds after an input change of state simply by doing arithmetic on the low order bits of the CST timestamps. The CST feature then performs the synchronization of outputs with inputs for you with a high degree of precision.

If a fuse is blown in an output-fused module, this option attaches a CST Timestamp to the Fuse Blown fault, indicating when the event occurred.

The timestamp reflects the time that the module detected the fault; if several faults occur in one message period, the timestamp reflects the time the last one was detected.

You can compare this timestamp with the current CST in the chassis containing the module in order to compute exactly when the fuse blew.

The module returns diagnostic data (For example, Fuse Blown, No Load) along with a CST timestamp of when the diagnostic data changes state.

The high volume module hardware has up to four input signal connections multiplexed to one analog-to-digital (ADC) converter.

Each input channel uses two wires connected to two hardware channels. The instrument measures the signal difference between the two wires.

This mode provides only two channels per ADC (versus four in single-ended mode), but generally offers a cleaner input signal to measure.

Differential Mode uses two signal connections for one signal to be measured, giving cleaner signals because of the differential measurement, and running twice as fast as Single Ended Mode because the ADC is timeshared between two signals instead of four, this also results in only half as many signal channels. For maximum speed, do away with the multiplexing altogether and just connect one input wire continuously to one ADC, eliminating the time lost to multiplexing and sharing, but ending up with only a quarter as many signal channels.

The high volume module hardware has up to four input signal connections multiplexed to one analog-to-digital (ADC) converter.

Multiple input channels are multiplexed to one analog-to-digital converter. For the highest possible conversion speed, one of those channels goes straight through to the ADC and the other three are ignored; however, faster sample rates are possible.

The high volume module hardware has up to four input signal connections multiplexed to one analog-to-digital converter (ADC).

Each channel uses one hardware channel. Four of these channels are multiplexed to one ADC.

In Single Ended Mode, the ADC switches between each of the four inputs, sampling each one. This yields more channels, but is slower because of the multiplexing.

Single-Ended mode offers the most in use input points per module, but at slower sampling speeds, and at the cost of a shared common per four-channel group.

You have to deactivate the alarm features if you want to get 16-channel floating point configuration. This setting reminds you that the alarm features are not available.