SMAR HI302, User Manual

Page: 42 / 92

Operation
5 . 8
Sequence for HVT Reading Cycle
After defining, executing and loading all of the configurations in the HI302, it is now
possible to communicate with the devices using the HVT block. The respective HIRT
block should have already identified the device before the HVT operation.
The HVT block operation is very simple and its use must comply with the following rules:
1. The user’s applicative must check if the block is available and reading the
BLK_EXEC_STATE parameter. If the parameter is set on UPDATING, the block is in
operation and cannot be used for a new transaction.
2. Write on the DEV_TAG_SEL parameter the 8-character TAG of the HART device that
one wishes to access. It must be the same as on the HIRT.HART_TAG parameter;
3. After writing on the HART_TAG, the block automatically checks if the command
configuration desired is in the memory. Otherwise, the block goes to HCD ERROR.
4. If there is one, the block checks if the TAG belongs to a HIRT block that corresponds
to a device installed in one HI302’s channel. If the TAG was not found, the status will
be TAG NOT FOUND and the process will be aborted.
5. If the HCD block and the HART_TAG were found, the parameter goes to UPDATING
and the communication process with the HART device begins. Thus, all of the reading
commands will be sent according to the sequence in the configuration
(HIRT.HCD_SEL [2] parameter).
6. If the device does not respond at the first command, the BLK_EXEC_STATE
parameter changes to NOT RESPONDING.
7. If the device responds at the first command, the status will continue on UPDATING
until the last reading command is sent. If there is an error during the communication,
the BLOCK_ERR will report it and the process will not stop until the last command is
sent. The block status will be PARTIALLY UPDATED and the user should identify the
problem, which may be a command configuration error or a non-compatible version.
8. In case the process finishes with no error, the block status will be UPDATED. Thus,
the applicative can read all of the block’s parameters according to the allocation map.
Writing Sequence in HVT Block Parameter
In order to write in a HART variable that is mapped as the HVT block parameter, the user
should perform an updating, that is, a comprehensive reading operation. When the HVT
block is UPDATED, follow the same procedure used for writing on HIRT blocks.
IMPORTANT
All the HVT parameters accept reading and writing. However, only the parameters that
have writing configuration will generate a HART transaction. The device should support
the command configured, even if the HI302 has started a writing transaction. So, if any
writing error occurs, check the HVT allocation map to make sure that the parameter is
mapped for a HART variable that can be written. Check if the corresponding
HCD_SEL[2] has the right value for the device.