Technical data

RS485 and RS232 Adapter Installation and Start-up Guide 4-1
Chapter 4 – Communication
This chapter describes the Modbus communication on ACS 160 drives.
Introduction to Modbus
Modbus is a serial, asynchronous protocol. The Modbus protocol does not
specify the physical interface. Typical physical interfaces are RS232 and
RS485, both of which are supported by the adapter.
Modbus is designed for integration with Modicon PLCs or other automation
devices, and the services closely correspond to the PLC architecture. The
ACS 160 drive ‘looks like’ a Modicon PLC on the network.
If detailed information regarding the Modicon Modbus protocol is required,
contact your ABB supplier for a copy of Modbus Protocol Guide.
Register Read and Write
The ACS 160 has all drive parameter, control and status information mapped
into a 4xxxx register area. This holding register area can be read from an
external device, and an external device can modify the register values by
writing to them.
There are no setup parameters for mapping the data to the 4xxxx register. The
mapping is pre-defined and corresponds directly to the ACS 160 parameter
grouping.
All parameters are available for both reading and writing. The parameter writes
are verified for correct value, and for valid register addresses. Some
parameters never allow writes (including Group 1 actual values), some
parameters allow write only when the drive is stopped (including Group 99
setup variables), and some can be modified at any time (including e.g. Group
22 acceleration and deceleration ramp times).