SMAR HI302, User Manual

Page: 40 / 92

Operation
5 . 6
2. If the parameter can be written, the writing request is started and the next transaction
with the device is waiting. The writing request has priority over HART transactions
since the block is set on UPDATED. The block status, in this case, goes to WRITING.
3. As soon as possible, the writing command will be set according to the definition in the
corresponding HCD block and will be sent to the device.
IMPORTANT
Despite the fact that the HI302 has responded and the writing was successful, the value
read on the parameter continues to be the old one. The new value is in a temporary
variable and the parameter will be updated after the writing confirmation in the HART
device.
4. In case the device does not respond, there will be attempts according to the schedule
in the HCFG.RETRIES[CHANNEL] parameter. If there is any message saying that the
writing was not performed, the HI302 will ignore the writing request. Even though the
device does not respond to the writing command, the HIRT block will always return to
UPDATE.
5. If the writing command response is positive, the block parameter is updated with the
new value written in the device. Then, the monitoring will read the new value and
finish the writing process successfully. The block status will go to OLD DATA and
then, to UPDATED. Thus, the ST_REV will be incremented.
6. Note that the time for a writing request can vary a lot:
•
If the channel is free and the writing request was immediately processed, the
transaction will last approximately 3s, provided there is no communication error
due to the time to send the writing command, read the value and send the
command to reset the device’s alteration flag.
•
If the channel is busy, the request will wait until the next time to be transmitted. A
long timeout is needed, if the transaction that is using the channel has several
retries and each retry has many repetitions. So, the user should monitor the
BLK_EXEC_STATE parameter.
IMPORTANT
This procedure indicates that the user’s application should monitor the
BLK_EXEC_STATE parameter. This parameter changes to WRITING, then to OLD
DATA and finally it goes to UPDATED provided the writing was done successfully.
At the same time, the parameter value (after the block has returned to UPDATED)
should be compared to the written value. So, the operation will be confirmed or not.