Section 7.4 Module Specific Commands; Get Hart Device Information - Spectrum Controls 1769sc-IF4IH User Manual

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Compact IO™ Isolated HART Analog Input Module
Section 7.4
Module Specific
Commands
User' s Manual 0300215-03 Rev. A
The HART input module uses module specific commands. Module specific commands
include the HART pass-through, HART suspend and resume, and get HART device
information. The commands are passed to the module using the input and output image.
Since some messages can be as long as 257 bytes, the data is transported to and from the
module 40 bytes at a time using the paging scheme described in the previous section.
The module specific command and accompanying data is passed to the routine in Figure
7-8 using a JSR instruction with parameters. When the routine is executed it will send
the message to the module. The response data if any is also converted by this routine and
stored in a temporary array where it can be used within the ladder program. See figure
below.
Figure 7-9 (Message Flow)
JSR
Input Par: Message Size
Input Par: Message Body (i.e. Device Specific Command)
Return Par: Message Done
Return Par: Message Response (i.e. Temp Array)
The tables on the following pages show the format for each module specific command.

7.4.1 Get HART Device Information

The Get HART Device Information command is used to gather the device specific
information for the connected HART device. The data that is retrieved can be seen in
Table 7-11. The information that is gathered by this command is similar to the
information gathered from the auto-acquisition process. The key difference is that the
Get HART Device Information command pulls the data that has been stored in the module
RAM and not directly from the field device.
Table 7-9 (Get HART Device Information Command)
HART Get Device Information – command message packet structure
Get currently cached Device Information for a given channel.
Field
HART Channel
Number
Command Number
Value
0x00 – 0x03 (1 byte)
0x03 (1 byte)
Routine
Fig 7.9
Definition
Module input
channel number for
HART command
The command
number to obtain
HART device
information