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Philips VI21
Philips’s new data-communication interface module, called the VI21, lets you include its PC20 programmable controller system as a master in hierarchical networks using the standard PPCCOM protocol. Depending on the VI21’s configuration, the PC20 system can act as a master for up to 16 slaves or as a slave for a host system, which can be a personal computer, VMEbus system, or another PC20. The support program contains a library of macros that help you control the data transfer between the PC20 and VI21.
The module communicates with PC20’s data memory via the I/O bus and with other devices via its RS-485 interface. It allows data transfers in blocks of up to 128 nibbles at a rate of up to 19,200 bps.
In one PC20 system, you can configure up to four VI21 modules as masters, allowing you to connect a maximum of 64 slaves. A PC20 with VI21 in slave configuration can be the master of another network with members of Philips’s programmable logic controller family.