ICC MBP-100, Instruction Manual

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14. Protocol-Specific Information
This section will discuss topics that are specific to each of the available network
selections.
14.1 Modbus
The gateway supports Modbus slave and master functionality via Modbus RTU.
The slave implementations share common access methods, which is to say
they support the same functions and reference the internal points via a
common “Modbus Slave” register assignment. Other notes of interest are:
•
Points are addressed by their assigned holding register (4X reference) or
input register (3X reference) via Modbus slave protocols.
•
Points can access both holding registers (4X references) and input
registers (3X references) via Modbus master protocols.
•
Supported Modbus slave functions are indicated in Table 3.
Table 3: Supported Modbus Slave Functions
Function Code Function
1 Read coils
2 Read input status
3 Read multiple registers
4 Read input registers
5 Write coil
6 Write single register
8 Diagnostics (subfunction 0 only)
15 Force multiple coils
16 Write multiple registers
•
Register number entry radix is decimal (e.g. 10 = 10
10
)
•
Configuration tip: Improved network utilization may be obtained by
appropriately grouping points into blocks having contiguous register
assignments. In this way, the “read multiple registers”, “read input
registers” and “write multiple registers” functions can be used to perform
transfers of larger blocks of registers using fewer Modbus transactions
compared to a situation where the read/write registers were arranged in an
alternating or scattered fashion.