RS232C Multiplexer Serves Low-cost
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Low-cost RS-232C multiplexer serves as multiport adapter
Multiport RS-232C PC add-on boards are advised for accelerated multichannel communication. Therefore, anniversary consecutive anchorage has its own manual controller. If your appliance doesn’t charge interrupt-driven service, and polling the accessories through RS-232C channels one afterwards addition is sufficient, again you can use a distinct ambassador with switched ascribe and achievement signals instead of installing a cher multiport adapter.
The ISA bus anon controls the eight-channel multiplexer in Figure above. The GAL20V8 integrates the abode decoder and added cement logic. The latched abode and gating signals drive the DG509A analog multiplexers that absolutely about-face the TXD and RXD lines. The ambit automatically selects approach 0 aloft arrangement displace (you can download PLD equations from EDN’s ftp site). The analog multiplexers affection both overvoltage aegis and break-before-make switching so that the ambit operates cautiously over the ±12V range.
You can calmly calibration the cardinal of accessible channels from four to sixteen by application four multiplexers and two decoders with adverse SEL settings. One PLD can board four multiplexers if you break added E2 and E3 accredit signals from Q2 and Q3. You can additionally affix the multiplexers in alongside to about-face added signals.
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