Rockwell Automation 160IB1 InterBus Communication Module - Manual (Page 22)

5–2 InterBus Parameter Descriptions and Data Protocol
InterBus Data Protocol
Data Channels The data transfer in Interbus terminology is called Peripherals
Communications Protocol (PCP).
Process data and parameter data is transmitted in the InterBus system
via two independant transmission channels. i.e. the process data
channel and the parameter data channel.
The process data channel cyclically transmits process data in the
form of an I/O image. This image contains the logic control word to
start /stop the drive, and the reference to control the speed, which is
used in the application program to control the drive. Additionally this
image receives the drive status word, and the speed feedback word,
which is used in the application program to monitor drive operation.
Together with a diagnostics register, this results in three registers
being transmitted to and from the drive (see table 5 A & B). This
direct memory access to control the drive is both simple and quick.
The parameter data channel only transmits data if necessary, and is
integrated into the transmission protocol being handled by the
InterBus master. When the parameter data channel is used, the master
inserts a frame of information to send to the drive requesting different
actions (see table 5E). This frame of information requests a read or
write parameter/attribute which can take several physical cycles of
read/write with handshaking to implement, resulting in much slower
access than the process data channel.
Thus the combination of the faster process data channel for control,
and the slower parameter data channel, optimises the data
transmission.
Data from InterBus Master to
IB1 Slave A scaling factor is required to interpret a speed reference in RPM.
The 160 Drive parameter P66 - [Preset Frequency 5] is used by the IB1
Module for this purpose. See “160 SSC Drive Parameters” on page1.
Table 5.A
!
ATTENTION: Unpredictable motor speed can cause
death, injury or equipment damage. Do not use P66 as the
[Preset Frequency 5] function via control terminal wiring.
Register No. Register (Words) Description
0 Control Word According to DRIVECOM 20
1 Speed Reference Speed reference in RPM
2 Diagnostics reserved