Sigma IC-Modbus - Reading 32 Bit Integer values from two 16 Bit registers.

[Product_Support]

Issue

How to read a 32-bit integer value stored across two 16-bit registers using IC-Modbus.

Product Line

Satchwell BAS & Sigma

Environment

• IC-Modbus
• IC3-Modbus

Cause

Prior to firmware release 4.05, IC3-Modbus did not natively support reading 32-bit integer values directly.

Resolution

IC3-Modbus 4.05 and Later

Firmware version 4.05 introduced support for reading 32-bit values using Function Codes 03 (Read Holding Register) and 04 (Read Input Register).

Supported 32-bit data types:

• Signed 32-bit
• Signed 32-bit (swapped)
• Unsigned 32-bit
• Unsigned 32-bit (swapped)
• Float 32-bit
• Float 32-bit (swapped)

🔹 Note: This is a special case of the “2 register read” and requires two consecutive Sigma object numbers.

Refer to: Sigma - Release 4.06 - Firmware IC3-Modbus Release Note Section 11.4.2 – 32-bit Data Types

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Other Sigma Versions (Pre-4.05)

To read a 32-bit integer from two 16-bit registers:

1. Read both registers into separate Analogue Input (AI) objects.
2. Combine the values using a programmable object:
   • Multiply the high register by 65536
   • Add the low register value

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💡 Example Code Snippet

10 XFlo = POINT 0|64      ; High register
20 YFlo = POINT 0|65      ; Low register
30 ZFlo = (XFlo * 65536.0) + YFlo
40 RETURN VIA TEXT 200 VALUE ZFlo  ; Use a suitable text object

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Notes

• Ensure the register order (high vs. low) matches the device’s Modbus specification.
• Use Text 200 or a similar object to display the final 32-bit value.