User Manual

Compact IO™ Isolated HART Analog Input Module
U ser 's M a n u a l 0 300 21 5- 03 R ev. A
7-30
Sec t ion 7.4
Module Specific
Commands
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 co mmands ar e p a ssed to the module using the input and output i mage.
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 instruct ion 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)
The tables on the follo wing pages show the format for each module specific co mmand.
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 t hat is gathered by this com mand is similar to the
information gathered from the auto-acquisition process. The key difference is that the
Get HART Device Informatio n 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 Informatio n – command message packet structure
Get currently cached Device Info rmat ion for a given channel.
Field Value Definition
HART Channel
Number
0x00 – 0x03 (1 byte) Module input
channe l number for
HART command
Command Number 0x03 (1 byte) The command
number to obtain
HART device
information
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)
JSR
Routine
Fig 7.9