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| Point Type |
| Conditions that will trigger a COS report |
|
|
| point status change (e.g. override) |
| AI |
| change in alarm or warning status |
|
|
| NB: no value changes within the normal band are reported by COS! |
| AO |
| point status change (e.g. override) |
|
| NB: no value changes within the normal band are reported by COS! | |
|
|
| |
| BI, BO |
| point status change (e.g. override); includes current value (On/Off) |
| ADI, ADF, BD |
| none; COS cannot be used with internal data types. |
Using Override and Release – N2Open
It is not normally necessary to use the Override command explicitly as the FieldServer automatically uses this command when the Current Value attribute of a point is written. For any other attribute it uses the Write command. It will sometimes be necessary to send a Release command to an overridden point, however. To do this, a Map Descriptor must be configured with Function set to wrbx and MN2_Function set to Release. Then, when any value is stored to the Map Descriptor data location, the Release command will be sent to the N2Open point specified by the Map Descriptor.
4.4.2.2.VMA Map Descriptor Parameters
Column Title | Function | Legal Values | |
| Name of Node to fetch | One of the node names | |
Node_Name | specified in “Client Node | ||
data from | |||
| Descriptor” above | ||
|
| ||
|
| AI, AO, DI, DO, Driver | |
Data_Type | Data type | (used for ADF, ADI and | |
|
| BD) | |
|
|
| |
Length | Length of Map Descriptor | 1 | |
Address | Starting address of read | ||
block | |||
|
| ||
| Data type specifier to be |
| |
MN2_Type | set when Data_Type has | ||
| been set to Driver |
|
ADI, ADF and BD types: using the “Driver” Data_Type and MN2_Type fields
The VMA protocol uses a byte value to specify the data types. The standard types AI, AO, DI and DO correspond to a byte value of 1 through 4 respectively. The types ADF, ADI and BD are believed to correspond to a byte value of 5 through 7 respectively. If the user wishes to use any other type value based on knowledge of a particular VMA configuration, then that value may also be specified here. Refer to Section 4.4.5 for a specific example.
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