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Example 3 : Action Bits
Instead of having the driver store a value to indicate the action, the driver can set a bit, whose offset indicates the underlying action. For example, if the string ‘Fire Alarm in’ is contained in the action field of the message the driver would set the array element at offset 11 (use table 6.5 to get the value vs. string) to 1.
Important to note is that the driver does not clear a previously set bit when a new action is reported. Thus if two messages were received and the first reported ‘Fire Alarm in’ and the second reported ‘Supv. Event in ‘ then first the array element at offset 11 would be set to 1 and then element at offset 12 would be set. The element at offset 11 would remain set. Both would then remain set until a system reset is performed, the state of the point returns to normal (status:NORMAL) or you clear the bits by writing to the array from the remote device.
As the driver may use up to 100 consecutive array locations for each Ckt/Device pair, if you use this method of storing data you will need one map descriptor for each Ckt/Device pair. In this example the map descriptor will store data for Ckt 128 device 10 only. This is indicated by the Ckt number being set to 128, the device number being set to 10 and the length being set to 1.
If the driver doesn’t recognize the action type then it will set the array element at offset zero.
Map_Descriptors |
| Data_Array_Name | , | Data_Array_Offset, | Function, | Node_Name, | Ckt, | Dev, | Length | , | Data_Type | , | Clear_On_Reset | ||
Map_Descriptor_Name, | |||||||||||||||
Ckt1128_data12 | , | DA_ACTION_BITS | , | 000 | , | passive , | panel1 | , | 128, | 10 , | 1 | , | Action_Bits | , | yes |
Only one device per map descriptor.
Ensure that at 100 elements of data array are available for each map descriptor. ( 100 is the maximum action number.)
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