IL17574C
Page 5-4
Effective Date: 2/04
IQ 300
Page 5-4
Effective Date: 2/04
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The register data in the response message are packed as two bytes per register.
For each register, the first byte contains the high-order bits and the second contains
the low-order bits.
Because all of the data in the IQ 330M is stored as a 32 bit signed integer, you
always want to retrieve two registers to get the result. See below for an example.
One item is made up of 4 bytes of information. Using table 5.1 locate the MODBUS
address of 1804, this is the numeric object or item for I
B
. Each item (in this example
I
B
) equals 2 registers. Each register equals 2 bytes, therefore 1 item (I
B
) equals 4
bytes.
There are two locations that are not 32 bit signed integers, “status cause” and
“product ID”. These two locations will give valid single register (two byte) response
and respond in the following formate.
Field Name
Example
(HEX)
Slave Address
TBD
Function
04
Starting Address Hi
18
Starting Address Lo
03
Number of Points Hi
00
Number of Points Lo
02
Error Check (LRC or CRC) --
Table 5.2 Example Messages
Table 5.3 Example Responses
Field Name
Example
(Hex)
Slave Address
TBD
Function
04
Byte Count
04
Data Hi (Bits 15 thru 8)
01
Data Lo (Bits 7 thru 0)
02
Data Hi (Bits 31 thru 24)
00
Data Lo (Bits 23 thru 16)
0A
Error Check (LRC or CRC)
--
