Spectrum Controls 1734sc-IE2CH - Manual (Page 44)

4-4 Point IO™ 2/4 Channel Analog HART Module
User’s Manual Pub. 0300257-01 Rev. A
Section 4.3
Supported HART
CIP Messages
CIP messages can be sent to the module using the MSG instruction to retrieve additional
HART information that is not included in the module’s input tags. This data may
include, additional HART device information, HART device extended status, HART
pass-through messaging, or the ability to temporarily suspend/resume HART
communication on any given channel. The available HART CIP messages include:
Topic Page
Read Additional Device Status 4-4
Get HART device information 4-6
HART pass-through messaging 4-9
Flush Queue 4-14
Suspend HART communication 4-14
Resume HART communication 4-15
4.3.1 Read Additional Device Status
Most devices support HART command 48 which allows the HART primary or secondary
master to read additional device status information. HART command 48 is optional for
devices running HART revision 5 & 6, but is required for devices running revision 7.
Command 48 returns up to 25 bytes of status information. This group of 25 bytes
includes both pre-defined status bytes and device specific status.
The IExCH will keep an internal cache of each channels Command 48 status data and
make the data available via a CIP unconnected message. The IExCH keeps the data up to
date by monitoring the MSA (More Status Available) bit (i.e. bit 4 in the Field Device
Status Byte). See Error! Reference source not found. and Error! Reference source
not found. for more information. When the MSA changes state (i.e. changes from 0 to 1
or 1 to 0), the module will resend command 48 on the associated channel. If the MSA bit
remains set, the module will resend command 48 to the device every 2 minutes.
The SUA (Status Update Available) bit is used to notify the user that additional status for The SUA (Status Update Available) bit is used to notify the user that additional status for
the channel has been refreshed by the module and the user should re-send the “Read
Additional Device Status” CIP message to retrieve the cached data. After the CIP
message is sent, the bit will clear.
Note: The data returned by the “Read Additional Device Status” message
is in the original order as received from the HART device which means any
multi-byte elements in the data will be reversed in the PLC. Hart format is
MSB first and the PLC is LSB first for multi-byte variables. Since the
location of the multi-byte elements can vary depending on the device, the
module will not be able to reorder the bytes. Refer to the HART device’s
documentation for the location of each multi-byte element and reverse the
order of the bytes in ladder to interpret.
The module will update its internal data cache for command 48 under the following
conditions:
1. Initial device connection.
2. Detection of “more status available” bit change (0 to 1 or 1to 0).