UART Question...

[Eric Nelson]

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. :rolleyes:

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? :confused:

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

[Ken Roach]

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.

[rsdoran]

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.

[Eric Nelson]

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

beerchug

-Eric

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