This firmware version is intended for any user of the FMC firmware that does not use landing modules for synchronization of DO setpoint or AO mode dataset output writes. This version of the firmware allows output -only datasets for writes from DeltaV, preventing overwriting of output data by input read-backs prior to transmission to VIM.
The VIM on booting, or following an upload/download, processes all datasets and tests these to determine if they match the required properties for the purpose mapped in the VimNet configuration upload. During these test previous versions required the datasets assigned to DO SP and AO Mode to be output with read-back, the new version (2.2.0) also allows these datasets to be configured as output only. Now, if the dataset is configured as output only a flag is set and further processing of the data written from DeltaV is modified to expect any value in the high word of the 32-bit register, rather than the zero (0) value previously. This allows the sending of the same value in the lower word multiple times as is required for some FMC commands. Also no updates are made for return to the controller.
The values that were displayed in this (Ack, Nack, and TO) are also displayed in VimNet diagnostics, and in logger messages if enabled. To allow uses to also see these values, the firmware has been modified to allow the DO and AO status datasets to be configured as either 16-bit or 32-bit. Previous versions required these datasets to be configured as 16-bit, and held the field status value for the tags. If configured as 32-bit, the low word will hold the field status, and the high word will hold the Ack/Nack/TO status previously returned to DeltaV in the DO SP and AO Mode registers.
For current configuration in DeltaV changing the DO SP and AO Mode datasets to output only will be sufficient to modify the operation of the VIM. Now any change to the registers in these datasets will trigger writes to the VIM (and to the field). It is recommended that the high word is used as a sequence to force a write whether the actual value in the low word of the register changes or not. The high word will not actually be required to be modified if the low word changes, however changing it will enable the re-writing of the same value. The VIM ignores the high word in the register if the dataset is output only.
If it is desired to see the field “write” status in DeltaV, then the DO and AO status registers in DeltaV may also be changed to 32-bit. Following the download from controller, the VIM will continuously update the high word in these registers with this status as well as the field status received (in the low word).
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