Yaskawa Modicon 800 Series Remote I/O Network for use on Microtrac LAN - Manual (Page 15)

3 SOFTWARE
14 PLC Programming for GETN & RDCI PAC Blocks
5/24/96
PLC
Programming
for GETN &
RDCI PAC
Blocks
The following describes the programming technique suggested for use when
the PLC is used to update drive parameters in addition to other remote devices
such as the Remote Display Keypad. In the example illustrated, the PLC can
modify a parameter called “Master Line Speed”. This parameter is also
accessible through a Remote Display Keypad as menu item number 6 on the
fifth Remote Display Unit. The subsequent programming techniques make
sure that a change from one device is reflected at the other device and establish
when one device takes precedence over the other.
Within the PAC program, the RDU and PLC initialization commands
coordinate the multiple source parameter exchange. The PLC software must
also help coordinate this multiple source exchange.
There are four major elements to consider when using the PLC Initialization
command: the PLC, the PLC gateway, the drive, and the remote display
network.
The drive contains the PAC program which establishes the parameters. There
are two basic types of PAC blocks which can be used with the PLC
initialization command. These are the GETN and RDCI blocks which allow
the programmer to define functions for the PCDU. These PCDU functions can
also be accessed by devices on the drive network such as the PLC gateway.
The only difference between the RDCI block and the GETN block is the way
Figure 4. P L C Initialization Hardware and Signal Flow
RD 3004-20