Model 365 Application Notes



Data processing equipment in the office, on the factory floor and across the campus may come in a variety of 'flavors,' embracing terminals, badge readers, alarm equipment and all types of manufacturing and laboratory instruments. The serial EIA-232 interface is perhaps the most widespread interface found on different data devices. It is perhaps the most universally found debarkation point for bringing data into and out of these devices. Data communication connections between such equipment in the premises environment can often be accomplished by merely connecting interfaces together by a cable.

One problem arises though. While the EIA-232 interface is the most widespread interface, it is not ubiquitous. There are other interfaces, notably RS-422 and RS-485. The need often arises to interconnect data devices having different interfaces. Usually this need is to interconnect a device having the popular EIA-232 interface with a device having something else like RS-422.

Interface conversion is a straightforward task. However, when you have a heterogeneous environment with different types of equipment having different types of interfaces the whole management problem begins to get 'messy.' The network manager would like to have one interface converter type around to use in these situations and use it for whatever type of conversion is needed. The Model 365 is a neat solution to maintaining control and avoiding a mess.

The Model 365 allows conversion between EIA-232 and either RS-422 or RS-485 in just 1 box. The user simply selects either RS-422 or RS-485 for the conversion. Furthermore, the user can select either 2 or 4 wire RS-485. The universality of this converter goes even further. If RS-485 half duplex is desired for conversion the Model 365 can be configured to control data flow in either of two ways. It can use RTS of the EIA-232 interface or it can turn on when TD is applied to the EIA-232 interface.

The Model 365 can even give you further flexibility in configuring your premises data communications network. It may be that you have procured or inherited all data devices with the same interface and that this interface is the widespread EIA-232 interface - what else? You put these inherited devices aside in some storage area. However, some time later you (and the emphasis is on 'you') decide that you need to interconnect these types of devices in an RS-485 type 'polling' network. You realize that your inherited devices do not have the RS-485 interface demanded. But, you also realize that the Model 365 placed at each of your data devices gives it an RS-485 interface and allows you to implement the network you want and without having to go out and buy expensive data equipment with the needed interface built-in.

This is exactly the situation in the illustration. Here we have a minicomputer on the left, a plotter in the center and two terminals on the right. They were all inherited by a laboratory manager in a well-known company. Each of these devices only came with the EIA-232 interface. After some period of time the laboratory manager decided that for his installation a network was needed where a minicomputer would control a plotter and communicate with two terminals and that the control and communication would be effected by a polling protocol. RS-485 networking was perfect for this situation. However, the laboratory manager did not have data devices with the RS-485 interface. He also did not want 'to bust' his annual budget by going out and procuring new devices that had this interface. Instead he went to his storage area and pulled out the inherited devices with the EIA-232 interfaces. He then went and purchased a Model 365 to attach to each data device and gave it an RS-485 port - an inexpensive solution to his networking needs.
  

 

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