UART Question...

I'm getting tired of the constant cable-swapping zzzzz so I'm adding a few additional serial ports to my desktop (Having only 2 just doesn't cut it anymore).

While shopping around, I see that I have a choice of specifying 16550, 16650, or 16850 UARTs. Of course, as the size of the buffer goes up, so does the cost.

I only use these serial ports for communication to PLCs, HMIs, servo drives, etc. (you know, the stuff we program for a living), and rarely need to exceed 19.2 kbps.

So my question is: Does it really make a difference which UART I choose? IOW, are there any advantages (that I'll notice?) by having a larger buffer?

With the lack of Legacy ports on many new laptops, there's been a lot of confusion as to which serial adapters (USB and PCMCIA) are compatible with which PLC hardware. Though my question shouldn't be related to this, I just don't want to get stuck with a useless serial card. mddr

TIA for any input,

-Eric

If you're connecting to Allen-Bradley products, especially if you're going to attempt the 1747-PIC driver in RSLinx, go with good old 16550 UARTs.

The biggest serial port expander I've seen tested was just a 4-port PCI expander. RSLinx handled those 4 ports fine.

I use an older Quatech 2-port PCMCIA card and its performance has been perfect with all applications (RSLinx and many ASCII and Modbus utilities) I've tried on it.

The thing you gotta watch out for is being capable of using more serial ports. A serial port needs an IRQ, do you have 2 more that you can allocate.

I know, you can use a PCI card that "should" eliminate that problem. Verify that everything will comply.

You didnt mention 16750 or 16950...shouldnt matter overall, they "should" be backward compatible. If you dont see a need for faster than 57.6kps than stick with a standard card but from the prices I have seen checkout if the 16750 and up can go below 115k, if so there is no reason not to try one.

http://www.byterunner.com/why.html

http://www.quatech.com/

Both those sites have info on the chips and cards.

Thanks Guys.... Exactly the responses I was looking for.
Just so happens I was looking at Quatech stuff!

beerchug

-Eric

P.S. Ron, that byterunner link was very informative!