Function Code 04： ： ： ： Read Input Registers (3Xxxx) - ICP DAS USA LinPAC-8000 User Manual

Modbus RTU／TCP Server User Manual for LinPAC / LinCon
Response PDU
Byte 0
Device Net ID
ID
[**] AO value is presented in a WORD signature = 2 Bytes.
： ： ： ： 
NOTE
Real value on the I/O module = (Response AO value) / 1000
Minus value (>0x7FFF) is presented in 2's Complement.
Here is an example of a query to read AO #3 ~ #4 in slot 5 of LinPAC (Net ID 6) :
Device Net ID
Function Code
Address Hi (Slot index 1~8)
Address Lo (AO start address)
Data Count
From above example, the response value of AO#3 is 0x138F , then we can get the real
value on the I/O module should be : 5007(=0x138F) / 1000 = 5.007 (V).
The response value of AO #4 is 0xEC79, and it's greater than 0x7FFF, that means we
have a minus value. The 2's complement of 0xEC78 is 0x1388 (= 5000 d),
So we can get the real value on the I/O module : -5000 / 1000 = -5.000 (V)
2-4. Function Code 04： ： ： ： Read Input Registers (3xxxx)
This function code is used to read AI values from I-8017 and I-87017 modules.
Request PDU
Byte 0
Device Net ID
ID
Ver : 1.0 (2009.04)
Byte 1
Function code
03 Response data length [**]
Request
Hi
Lo
Byte 1 Byte 2
Function code Address Hi
04 Slot Index (1~8)
Byte 2
Byte count
06 Device Net ID
03 Function Code
05 Data length (Byte)
03
AO #3 read back value
00
02
AO #4 read bacek value
Byte 3
Address Lo
AI Address
10
Byte 3 ～ (Byte Count + 2)
Response AO values
two bytes / pre AO register
Response
06
03
04
Hi 13
Lo 8F
Hi EC
Lo 78
Byte 4 Byte 5
Data count Hi Data count Lo
Data type[*] AI count
L2