The analog and digital I/O points on an Ethernet-based I/O unit return incorrect data values, even though from PAC Control debug mode, communication to the I/O unit is enabled and no errors are reported. Digital output points (on 4-channel digital output modules) cannot be turned on or off. Using PAC Manager to inspect the I/O unit’s point configuration indicates all digital points are inputs and analog points are set to default configuration and scaling, even though other selections had been previously configured. Disabling and re-enabling communication to the I/O unit or stopping and starting the strategy does not correct the issue.
Whenever an I/O unit powers up or resets, its Power Up Clear (PUC) flag is set. Until it receives a "Power Up Clear" command from a host device, the unit responds to any other command it receives with a "PUC Expected" error. This lets the host know that it has just powered up and may need to be configured.
When a SNAP PAC controller receives this response, it sends a Power Up Clear (PUC) command to the I/O unit, followed by a series of configuration commands. Once the PUC command has been received by the unit, no other hosts will receive the Power Up Expected error when they communicate with the I/O Unit.
However, if a host such as PAC Display, PAC Control debugger, PAC Manager, OptoDataLink, OptoOPCServer, or an OptoTerminal-G70 or G75 sends the PUC command to the I/O unit before the controller communicates with the unit, the controller will not receive the "PUC Expected" error, and will not know that the I/O Unit and I/O points need to be configured.
Opto 22 has resolved this issue.
Both the controller and the I/O unit(s) must have the new firmware. If either the controller or I/O has older firmware, the PUC flag will be used, so I/O will work exactly as it did before this update.
As part of commissioning a project, after the I/O has been configured, use PAC Manager to store each I/O unit’s configuration to flash by selecting, Tools > Inspect, Status Write > Store configuration to flash. By doing so, the I/O configuration resides on the I/O unit and is available should the unit reset or have power cycled to it.