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pmurray:
I put this poll under HAAS rather than at a general point, because HAAS since about 1998 has 115.2 kbaud capability.
HAAS provides Xmodem under RS232. This operates as you indicated.
Few people use Xmodem, but it would be better if it was used. Anybody using it please indicate this.
On HAAS if you use Xmodem, then you must select no parity and 8 data bits. I always suggest that you use 1 stop bit unless for some reason an RS232 source or destination requires 2 stop bits.
If you do not use Xmodem, then you should use parity, and 7 data bits. There is no need for 8 data bits. If you use 8 data bits then you transmit about 10% slower than with 7 data bits.
Single bit parity is an error detection method. This is the only type available in standard UARTs. The parity check is done on a byte by byte basis. A single bit parity check will flag any odd number bits in error in a byte. Thus, two bits reversed in a byte will not produce a single bit parity error, but three bits in error cause a parity error. For much analysis in information theory it is assumed that the error rate for two bits is the square of the error rate for one bit. With an error rate of 1 bit 100,000,000 bits you see the error rate is extremely low for two. Usually this is based on the noise being white Gaussian. This is not necessarily true in the industrial environment, but still you expect the two bit error rate to be less than the one bit rate.
If a greater number of parity bits are used, then more complex errors are detectable and some error correction is possible.
Note, Xmodem does not use a parity but rather a checksum over a block of bytes. On detecting an error Xmodem requests a retransmission.
On receipt of data HAAS flags errors it can detect. If parity is on, then this is one type of error.
If you are not doing DNC (meaning drip feed) then a very good error check on data sent to the CNC is to send the file back to the computer and do a file comparison.
I do not believe any HAAS machines provide a means to compare two programs in their memory. So to check a program sent from HAAS to a computer send the program twice and compare the two in the computer. What we normally do is a SEND ALL, then send each individual file. If we find a problem later, then we compare one with the other.
With a suitable interconnect system you can get very low transfer error rates without Xmodem, but Xmodem is better. I do not have a suggestion for an Xmodem program. We may have to write one.
In an environment that is not too noisy we can transfer 115.2 kbaud 4000 ft and actually functioned to 8000 ft, but the signal level is too marginal at that distance and baud rate.
This poll is not a sales pitch, and we will not contact anyone without their request. So we are not probing for names, and therefore feel free to mark all the different rates you use. The names that show up in the poll are useful to indicate multiple baud rate useage. What I want is to try to get a realistic response of what users are doing and why. There are no incorrect answers. The goal is to get relatively unbiased answers.
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