Spectrum Controls 1734sc-IE2CH - Manual (Page 46)

4-6 Point IO™ 2/4 Channel Analog HART Module
User’s Manual Pub. 0300257-01 Rev. A
Table 4-4 (Request Succeeded)
HART Read Extended Status - Reply packet structure
Offset Field Value Definition
0 Status 00 = SUCCESS (1 byte) Command status
1 Count 0-25(1 byte) Number of Status bytes
available
2-26 Additional Status Bytes Additional Status bytes
returned by CMD48
For Class Instance(Instance=0)
if device doesn’t return any or
all 25 bytes then the remaining
are set to 0.
27 Pad 0 Included if all 25 Additional
Status bytes returned or
returning all Channels at once
for Instance 0
4.3.2 Get HART Device Information
When a HART device is first connected to the module, the module will send a series of
HART commands to retrieve information about the device. This device information is
held in the module’s cache memory and can be retrieved by sending an unconnected CIP
message. The following table lists the commands that are sent by the module when the
device is first connected.
Table 4-5 (HART Initialization Sequence)
Commands sent at Initial device connection
Command: Definition: Comment:
0 Read unique identifier. Sent using “Short Address” to find device
6 Set Polling Address Only sent if device responded at non 0 Addr
59 Write number of response preambles.
12 Read Message
13 Read tag, descriptor, and date.
15 PV upper and lower range values
16 Read final assembly Number.
48 Read Additional Device Status
50 Read dynamic variable assignments.
3 or 9 Read Dynamic Variables Cmd 3 if HART rev 5, else Cmd 9 used
2 Read Loop Current Only sent if Cmd 9 is being used
If the connected HART device’s configuration changes, the device will set the
”configuration changed” bit (i.e. bit 6 of the Field Device Status byte). When the IExCH
detects that the “configuration changed” bit is high, it will automatically re-send the
appropriate HART commands to refresh the device information stored in its cache
memory. See Table 4-6. The first command sent is command 38 which will reset the
“configuration changed” bit in the device.
The CFG (device configuration changed) bit was added to the IExCH input assembly to