K-Sequence vs. DirectNet Protocol

There are subtle differences in the two protocols in terms of message content but the general flow of the packets is pretty much the same. In both cases there are about five interchanges between the PLC and PC to exchange a given piece or block of data. In a direct connection this back and forth between the PC and PLC is a small issue that introduces a little bit of delay.

As far as what protocol we prefer, we tend to side towards the DirectNet protocol if the given model of AutomationDirect PLC required supports it because DirectNet is an open, documented protocol and thus changes made to the protocol by the hardware manufacturer tend to make it to market faster than with K-Sequence. Our development team has the agreements in place to keep up with K-Sequence protocol changes, but the reality is that it doesn't happen as quickly as with DirectNet.

In a modem application, however, each time there is a change of direction in transmission the modem link will induce delay that makes the transfer perceivably  slower. Depending on the modem and the mode of operation(error correction, data compression), the additional delay per full transaction could be from 250 milliseconds to 600 milliseconds. It doesn't sound like a lot in the grand scheme of things but it can add up when you consider this is per transaction. The key of course with doing modem connections is to keep one's expectations reasonable, recognizing that the modems do introduce additional overhead.