Each port on the Serial Card contains a configuration item called Send Outputs On Startup that controls how outputs are handled on initial configuration of the Serial Card and during switchover for Series 2 redundant Serial cards. This feature applies only to output datasets. If this configuration item is not enabled in the serial port configuration, initial output values are not sent out to the Modbus devices connected to the port under any circumstances.
If Send Outputs on Startup is set then, in most cases, the card sends the current outputs to the serial devices on power-up, reset, download, and switchover. If a dataset is being configured for the first time, it is transitioning from the unconfigured to the configured state. In this case, the card sends initial values to the serial devices instead of current values.
If a Serial Card that was previously configured is downloaded again or partially downloaded, the initial values are not sent to the Modbus devices even if the Send Outputs On Startup configuration item is enabled. If a new output dataset is added to a Serial Card configuration and the card is downloaded again, initial output values for the newly configured dataset are sent to the Modbus Device, but any other datasets that were previously configured do not send out their initial values.
Specify the initial output values through the dataset registers. To access the register values, click the dataset in Explorer. The registers are displayed in the right pane with names like R1, R2, and so on. Right-click a register to enter an initial value.