ACH550-UH User’s Manual
155
Serial Communication – EFB
Faults 31…33 – EFB1…EFB3
The three EFB fault codes listed for the drive in "Diagnostics" starting on page 212
(fault codes 31…33) are not used.
Intermittent Off-line Occurrences
The problems described above are the most common problems encountered with
ACH550 serial communication. Intermittent problems might also be caused by:
•
marginally loose connections,
•
wear on wires caused by equipment vibrations,
•
insufficient grounding and shielding on both the devices and on the
communication cables.
Modbus Protocol Technical Data
Overview
The Modbus® protocol was introduced by Modicon, Inc. for use in control
environments featuring Modicon programmable controllers. Due to its ease of use
and implementation, this common PLC language was quickly adopted as a de-facto
standard for integration of a wide variety of master controllers and slave devices.
Modbus is a serial, asynchronous protocol. Transactions are half-duplex, featuring a
single Master controlling one or more Slaves. While RS232 can be used for point-to-
point communication between a single Master and a single Slave, a more common
implementation features a multi-drop RS485 network with a single Master controlling
multiple Slaves. The ACH550 features RS485 for its Modbus physical interface.
RTU
The Modbus specification defines two distinct transmission modes: ASCII and RTU.
The ACH550 supports RTU only.
Feature Summary
The following Modbus function codes are supported by the ACH550.
Function
Code (Hex)
Description
Read Coil Status
0x01
Read discrete output status. For the ACH550, the individual bits
of the control word are mapped to Coils 1…16. Relay outputs are
mapped sequentially beginning with Coil 33 (e.g. RO1=Coil 33).
Read Discrete Input
Status
0x02
Read discrete inputs status. For the ACH550, the individual bits
of the status word are mapped to Inputs 1…16 or 1…32,
depending on the active profile. Terminal inputs are mapped
sequentially beginning with Input 33 (e.g. DI1=Input 33).
Read Multiple
Holding Registers
0x03
Read multiple holding registers. For the ACH550, the entire
parameter set is mapped as holding registers, as well as
command, status and reference values.
Read Multiple Input
Registers
0x04
Read multiple input registers. For the ACH550, the 2 analog input
channels are mapped as input registers 1 & 2.
Force Single Coil
0x05
Write a single discrete output. For the ACH550, the individual bits
of the control word are mapped to Coils 1…16. Relay outputs are
mapped sequentially beginning with Coil 33 (e.g. RO1=Coil 33).
