Figure 2.3 shows a typical setup, with 16 devices sending information at random times to the PC. The switches at Level 2 receive the data and send it on to the Level 1 switch. The Level 1 switch buffers the data and sends it to the PC. Each of the switches will automatically send the data when it is available. If another port has access to the PC, the data will be buffered until a path is available.
Slave Devices that Automatically Send their Data:
For best results in an automatic system, the 232BSS4s in the system should be set up the following way.
•Set the switches to turn on the Auto Select feature.
•Set the Port Timer to 0
•Set the Inactivity Timer on all of the switches to somewhere between 20 and 500 milliseconds, depending on the space between data packets and the response time required to each connected device.
•If you need your software to identify which port sent the data, set up the port preamble on the Level 2 switches. Set each port to have a unique preamble. The preamble can be 1, 2, 3, or 4 characters long, and any characters can be used. The preamble will be added to the beginning of each new data packet arriving at the PC. The data collection software on the PC should be written to recognize this preamble as an address or identifier of the data source.
Documentation Number | 19 |
&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph
B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353
