Periodic Timer Module
When used together with other modules, the Periodic Timer allows you to make events happen on a regular basis. For example, when used with a Recorder module, the Periodic Timer can be used to implement a snapshot log.
This input enables or disables the Periodic Timer module. When the module is disabled, no pulses are generated on the Trigger output register. Linking this input is optional; the module is enabled by default.
This input defines the starting point at which the Periodic Timer module begins timing. When a pulse is received on this input, the Periodic Timer starts timing from this new starting point. This input is optional; if you leave it unlinked, it will never receive a pulse.
The setup registers of the Period Timer module determine at what point output pulses are generated.
This numeric bounded register specifies the number of seconds between pulses on the Trigger output register.
This register determines whether the Trigger output generates a pulse when the Sync input is pulsed (trigger on sync) or if it waits for the first period to expire (no trig on sync).
When the module is enabled, this pulse register generates a pulse every time the period specified by the Period setup register expires. If the Sync input is linked and you have set the Sync Mode setup register to trigger on sync, the Trigger output will generate a pulse every time the Sync input is pulsed, in addition to pulsing each time the period expires.
All events produced by a Periodic Timer module are written into this register. Possible events and their associated priority numbers are shown in the following table:
|Event priority group
|A module resynch has occurred.
|Input links, setup registers or labels have changed.
The Event output register stores the following information for each ION event: time stamp, priority, cause, effect, and any values or conditions associated with the cause and effect.
Responses to special conditions
The following table summarizes how the Periodic Timer module behaves under different conditions.
|Response of output registers
|If the Enable input is off
|No pulses will be generated at the output register.
|Pulses start when the module starts (goes online).
|When the module is re-linked or its setup registers are changed
|Pulses are generated as soon as the module goes online.
Detailed module operation
The following figure illustrates the operation of the Periodic Timer module with the Sync input linked or unlinked. The marks indicate when a pulse is generated on the Trigger output.
In all four cases, the Period is set to 900 s (15 minutes).
Note how the timing of the Trigger pulse is affected by linking or unlinking the Sync input. The Sync input controls whether the Trigger pulses occur on regular time boundaries (e.g. 7:45:00, 8:00:00, 8:15:00) or in-between (e.g. 7:37:45, 7:52:45, 8:07:45). Sync Mode controls whether a pulse is immediately generated when an Sync pulse is received (e.g. at 7:37:45) or if it is delayed.
To account for time zone and Daylight Savings Time information, the Periodic Timer module needs to refer to a clock. For ION meters, the Periodic Timer module uses the Local Time output register of the device’s Clock module. For the Virtual Processor, the Periodic Timer module uses the workstation’s local time.
If, for example, you set the Periodic Timer to pulse twice a day (i.e. once every 12 hours, or 43200 seconds), the module will pulse once at 12:00 midnight, and again at 12:00 noon (local time).