SMAR HI302, User Manual

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HI302 - User’s Manual
5.5
6. In normal operation, the alteration flag, located in the Response Code, is checked at each
transaction. If this flag is set, the HI302 starts a reading sequence on the parameter of the
HIRT block, that is, the BLK_EXEC_STATE parameter goes to IDENTIFICATION. The
HVT block does not update automatically and its ST REV parameter has no useful
meaning. At the end of the reading process, the block should be updated and reflecting
the device’s data. So, the ST_REV parameter of the corresponding HIRT block is
incremented and will indicate that a parameter was changed.
HART Variable Writing and Reading
An operation model, based on reading cycles and writing requests, was designed to make
the HI302 use as simple as possible.
HART variables Reading Cycles
The variable reading is always done in-group because of the HART command structure.
Therefore, the HI302 variable readings are done through cycles, that is, the HIRT block
always updates several parameters at the same time (except the writing). When the HVT
block is executed, all of the reading commands from the device configuration
(HIRT.HCD_SEL. [2]) are executed at the same time, following the configuration
sequence. See the Appendixes.
When the HIRT block detects any change in the device (BLK_EXEC_STATE=OLD
DATA), it starts an update process and sends the reading parameters of the configuration
selected in the HIRT.HCD_SEL [1] parameter. The applicative checks if the ST_REV was
changed and begun to execute the HVT block for the device.
Writing on parameters that map the HART variables
Unlike the reading, writing on parameters that map HART variables is done separately for
each device.
IMPORTANT
Not all parameters related to HART variables allow writing. The blocks that allow writing
depends on the device’s HART version. If the user has any doubt about writing on
parameters, check the HIRT block documentation as well as the HART commands
supported by the device.
Since some HART commands have variables for writing, the command will be composed
of the parameter to be changed and the parameters described in the command definition
(HCD block). As the parameter does not inform which HART command should be used to
write (The writing and reading parameters are not the same), it is necessary an additional
configuration for the parameters to be written. Such additional configuration is done in the
HWPC block because it has the correlation between these parameters and the HART
commands used for writing. The HWPC has the same code as the corresponding HCD,
therefore, the entire configuration for a HART device should have a HCD + HWPC pair. A
writing request starts a process with the following stages:
1. After the parameter had received the writing command, the HI302 checks the HWPC
block to know if that parameter can be written, that is, if it has a configuration to write.
If the parameter has such a configuration, the HI302 stores the value received in a
temporary variable and starts the writing process in the device. If the parameter does
not have this configuration, the HI302 returns a standard response indicating that the
parameter cannot be written.
IMPORTANT
In case the parameter does not accept writing, check if the HWPC configuration is
correct or the code programmed in HIRT.HCD_SEL[1] is correct.