RS232 problem sending with newer PC

[Al_The_Man]

For shops that have a PC's out in the shop used for nothing else but upload/download to thier CNC machines, (or some shops wheel one around on a dolly).
Windows is a major overkill, I have set up quite a few of my customers with one of the old DOS programs that are still around today, Telix being one, it is still shareware.
Now ver 3.51, if you use this you also need to search for the tlxmdm351.zip file to load in the same directory.
Al

[cogsman1]

The PC is TOO fast for the control. You need to see if your software has a setting to dwell after each line. I had this problem and my software (WIN-CNC) allowed for this setting. I use this on Citizen(Mitsubishi), Wasino(Fanuc) and Eurotech(Fanuc).

http://www.marucit.com/products/software/wincnc.html

[cadcam]

you need to look for an option for charitaor delay on the send option.

[gar]

050610-2025 EST USA

I find this thread somewhat confusing.

Also my comments are from a basic and generalist point of view.

First, For information on some aspects of how a UART works I would suggest that you goto http://www.freebsd.org/doc/en_US.ISO...s/serial-uart/ and at least read paragraphs 1 and 1.2, also look at my thread --- stop bits, parity.

When I do a preview of this post the freebsd address is displayed incorrectly, yet when picked it gets me to the location. Use MSN.COM search if necessary, no double quotes on my search words.

By the way, a search using Google did not produce useful results in the top few (these were mostly superficial). MSN was much better and produced the freebsd location. In both cases I seached using the words, something like --- how does a uart work .

Years ago how a UART works (may have had a different name circa 1970) was described in the datasheet for the device. Today the National Semiconductor datsheet for the 16550 basically assumes you know the general operation of a UART. To get to the National datasheet use www.national.com then enter 16550 in their search box. Next select .pdf datasheet and print it out.

Repeating what I have said many times --- the destination receiver stop bit setting must be less than or equal to the source transmitter stop bit setting. In practice with standard UARTs this means both source and destination must be set to exacaty the same number of stop bits.

Unless the system designers of the computers and/or the CNCs have done a poor job, then the flow rate should be controlled by your selection of a handshake protocol, rather than slowing the character rate by lowering baud rate or some other means. You should use the maximum possible baud rate controlled by other factors than buffer overflow.

However, there may be some hardware problems in non-licensed 16550 or equivalent devices. There is some discussion in the freebsd article.

In the use of standard UARTs (today meaning National Semiconductor 16550 or other legally licensed suppliers) it is possible to use a FIFO buffer in the UART or not depending upon a setting to the UART. The UART itself does not perform the handshake funtion, although the handshake signals are transferred thru the UART. This means at the receiving end there is no way to know that the receiving FIFO is getting full (you only know there is at least one byte in the receiving FIFO), and signal the transmitter to stop sending, and furthermore that would not stop anything already in the send FIFO buffer.

Apparently Fanuc and maybe others have too small of an input buffer following the UART or other processing problems to absorb the typical 16 bytes from a full UART FIFO transmitting buffer. Thus, you must set your UARTs to no FIFO, which really means a 1 byte FIFO. Inhibiting the source FIFO has apparenetly cured overflow problems for a number of CNC shops.

If you were to lower your baud rate, or add a delay between characters simply to avoid using a handshake, or finding out how to use it, then you are unnecessarily lowering your average data transfer rate and possibly slowing your CNC machine. And you may not solve the problem, especially in a DNC application.

The way any correctly working handshake works follows:

At the destination there is some buffer which is N bytes long. Usually this will be a circular buffer mod N.

There is a put and get pointer to this buffer and the difference indicates how full is the buffer (each pointer being mod N). The designer will set some criteria of fullness where the handshake stop signal is generated. This has to take into account expected handshaking delays.

At some lesser value of fullness the start signal is generated.

Hardware handshake will be very slightly faster than software, but if the N byte buffer is sufficiently larger than the source buffer, then you can operate at maximum baud rate and the flow is modulated by the rate the destination can receive and use data rather than by some arbitrary slow sending rate.

Note: delay between characters is the same as adding stop bits.

Now I have probably added further confusion, but that is not my goal. Rather I want you to get the most production from your machines. Recently I increased a customer's machine thruput by about 2 to 1 on a HAAS VF2 machining carbon electrodes in DNC mode by a combination of things including increased baud rate.

beta-a2.com

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