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DPI State diagram.

State diagram symbols

The state diagram shows DPI states as a result of power on, reset, battery fault etc. A circle indicates a permanent state, in which the DPI stays until an event triggers transition to another. An arrow indicates an event. A text on the arrow informs about the type of event. In some cases, an operation is performed by the DPI during transition between states. Such an operation is indicated by a rectangle. In some cases, the resulting state depends on a condition. A selector indicates this.

Power on

The initial state is No power. Connecting power to the DPI initiates state transition. First of all, it is checked whether RAM voltage has been too low during power off, so that the contents of RAM is undefined. This is checked by means of the built-in Real Time Clock circuitry.

If the RAM voltage has been too low, all RAM is initiated. If battery check is enabled (Service.DeviceConfig.EnableBit[1] = FALSE), battery error is indicated. Following that, the Init PP operation is initiated.

If the RAM voltage was OK, actual error on the service channel is cleared, provided it didn’t indicate battery error. The only way to clear battery error is to perform a reset by writing 255 to the Service.Reset variable, or pressing the reset button. If power was off for a shorter time than defined in the variable MaxPowerdownTime, the Process-Pascal program resumes from where it was prior to power loss. If the power was off for a longer time, the Init PP operation is initiated.

Init PP

The Init PP operation enables the softwire table for the selected Process-Pascal program, thus enabling access to the global variables in the program. If Autostart in the Process-Pascal channel is ON, the Process-Pascal program is started, resulting in state PP Run. If autostart is OFF, the resulting state is PP Idle.

PP Run

This is the normal, operating state, in which the Process-Pascal is running. Normally, 3 different events terminates this state.

If power is turned off, the Process-Pascal state is saved, making it possible to resume after power on.

If the DPI is reset by pressing the reset button shortly (less than 10 seconds) or by writing 255 to the variable Service.Reset, actual error on the service channel is cleared, and the Init PP operation is initiated.

If the DPI is master reset by pressing the reset button for more than 10 seconds, all RAM is initiated, actual error on the service channel is set to indicate master reset, default parameters are used for communication ports, and the resulting state is No PP. Configured parameters for communication ports will be used again following a reset or power down.

PP Idle

This is the DPI state entered if AutoStart on the Process-Pascal channel is OFF. It is also the state entered after download of a Process-Pascal program. Reset, power off or selecting Start on the Process-Pascal channel (for example by means of the VIGO Program Download utility) terminates this state.

No PP

This state is entered after a Button Masterreset, which is performed by pressing the reset button for more than 10 seconds. It is also the state of the DPI during download of a new operating system. A DPI holds 2 operating systems, a Boot OpSys which is active in this state, and a FLASH operating system, which is active in all other states. Reset, power off or selecting Start on the OpSys channel terminates this state.