plxvm/doc/events.md

Events

There are mainly three event classes:

1. System events
   • Device Events
   • Timer Events
   • Message Events
2. Signal events
   • Hardware
   • Software
3. User events

Note: Event names are restricted to four unique characters. Longer names are allowed, shorter than 4 characters are not allowed. All system events must be registered by the hist application:

AddEvent("class",index);

Device Events

Device events are registered by the host application. Each device event is characterized by a device class (e.g., ADC), and a device index (e.g., ADC 1). A device event handler is registered for a device class and a device index by using the on event(<class>,<devindex> call statement. Multiple handler procedures can be registered for one device class. The event variable can be used to identifythe specific device.

proc foo {
  if event=0: ... // ADC 1
  if event=1: ... // ADC 2
}
on event("adc",1) call foo 
on event("adc",2) call foo 

Message Events

Message events are registered by the host application, but raised by the network module.

Signal Events

Signals are commonly implemented by digital logic and used for inter-node communciation. Evens are sent by using the !> operator. There are commonly request broadcast and consent (barrier) signal protocols, assigned to signal 0 and 1, respectively. The signal logic must be provided by the host application.

event sig1=("signal",1)
sig1 !> 
sig1 ?   -- await event ("signal",1)

Timer Events

Commonly at least one timer (hardware or software) is registered. In contrast to other peripherial devices, a timer must be started by using the timer(<timerindex>,<millis>) statement. A timer is stopped by using the timer(<timerindex>,0) statement.

proc foo {

}
on event("timer",0) call foo 

User Events

User events are created by using the event definition statement. An event handler (a procedure) is registered for a user event by using the on call statement. Inisde an event handler the event number can be accessed by the event variable. Multiple events can be bound to one handler procedure. A user evenr is raised by the ! send operator without any argument and the event as the channel. User events can be used within a task or across tasks.

event <uevA>[,<uevB>,..]
proc foo {
  if event=<usev> then ...
}
on <uevA> call <foo>
on <uevAB> call <foo>
<uevA> !

Event alias

event <sysevA>=("class",index)
proc foo {
  ...
}
on <sysevA> call <foo>
await <sysevA> delay <timeout>
<sysevA> ? 

In-line Event Handling

In addition to event handler routines in-line event handling is supported using the await event statement. An await statement can be extended by a delay statement binding a timeout to the event awaiting.

await event(<evname>,<devindex>)
await event(<evname>,<devindex>) delay <millis>
-- Wait for timer event
timer(0,2000) -- start interval timer 0 with 1000 ms period 
await event("timer",0) .. wair for timer event

The event variable holds the event device index after an await statement or -1 if timeout or interuuption occured.