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Punch Code Format

 
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John_B
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Joined: 03 Jul 2004
Posts: 56
Location: Milwaukee, WI USA

PostPosted: Mon Dec 05, 2005 10:55 pm    Post subject: Punch Code Format Reply with quote

Does anyone know of a source for documentation on the format of punched paper tape for various machine manufacturers? (ie. Warner&Swasey, Cincinnati Milicron, SunStrand ....)

I have several machines of these types with executive paper tapes that are in bad condition. I would like to write software to read those tapes, varify the data against the specified format (checksums, parity, block length, leader length and etc.) and punch a new tape to replace them.
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franke
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Joined: 26 Jun 2004
Posts: 161
Location: Indiana, USA

PostPosted: Mon Dec 05, 2005 10:57 pm    Post subject: Reply with quote

We've had some experience duplicating "Exec" tapes for Cincinnatis as well as old Fanuc 200s. Exec tapes must be read and punched in pure binary, where any individual character on the tape can range from 0 to 255 binary (no holes to 8 holes across). Other types of ASCII or EIA tapes can be read and saved as normal ASCII characters.

We would always read the old Exec tape until we got a perfect binary match at least 3 times to avoid errors. When you save these files on a computer disk, you must also save them as binary files so your software does not mistake a binary 26 for an end-of-file marker on the disk file. When punching a copy of the tape, you must likewise read and punch in pure binary.

You can tell by looking at a paper tape what the coding is.

An EIA RS244 coded tape always has an odd number of holes across the tape (each character has either 1, 3, 5, or 7 holes across. Channel 8 is only used for the EOB code, which always just has one hole in channel 8

ASCII No parity tapes can have even or odd numbers of holes across, but channel 8 is never punched.

ASCII Even parity tapes always have even numbers of holes across, and all 8 channels are used.

ASCII Odd parity (rarely used) always has odd numbers of holes across, and all 8 channels are used.

A binary "Exec" tape can have any combination of holes (across the tape). All 8 channels are used for data, and some characters have even numbers of holes across and some characters have odd numbers of holes.
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JoeM
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Joined: 09 Jul 2004
Posts: 122
Location: Jackson Hole, Wyoming USA

PostPosted: Mon Dec 05, 2005 11:01 pm    Post subject: Reply with quote

I don't think these Exec tapes use any form of error correction protocol.

It's always been my belief that there's a small "bootstrap loader" program at the beginning of the tape, which is the software the CNC needs to read the rest of the tape. After that, the bootstrap loader program in the CNC starts and reads in the binary data. From what I've seen of these tapes, there may be a checksum, but it won't help you "fix" a bad spot in the tape. It will just tell you that it didn't read correctly.

On the old Fanuc 200s that I used to work on, a questionable Exec tape might read in several times before it let the control run normally. I've never heard of a way to fix damaged tapes, other than useing the old manual splicing techniques with stickers and tape and such.

If your tape is obviously torn or has buggered-up holes, it can be fixed manually. If the damage is too extensive repair manually, you may just have to spring for another tape.

You may find someone on this forum with an identical machine who would let you "borrow" an Exec tape for reproduction.
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franke
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Joined: 26 Jun 2004
Posts: 161
Location: Indiana, USA

PostPosted: Mon Dec 05, 2005 11:04 pm    Post subject: Reply with quote

Concerning Allen Bradley, GE and perhaps some other executive tapes, the computers are 16 bit machines and it takes two rows of 8 bit tape for a data word. There is no parity, rows can be odd or even because the data is machine language. Check sum was the usual method to detect errors.

An executive tape was usually two parts, the basic computer manufacturers data to tell the computer how to do all the basic functions required of a machine controller no matter what type of machine was involved and a second part that configured the CNC to the specific machine it was operating. The first part was written by the CNC manufacturer and didn't change much over time on a given control. The second part was written or adjusted by the machine manufacturer that applied the control to the machine. The second part was usually in EIA coding or ASCII coding and was parity checked. Sometimes this would be two separate tapes but Warner & Swasey usually spliced them into one tape. On GE CNC's the second section was call the MSD - for machine set-up data.

The second part of the tape with the machine data was specific enough to the machine that an exec. tape could not be used on a different size machine because the axis travel lengths, spindle RPM's and other data would not be the same. Even on the same size machine there were sometimes differences because external functions would be different addresses in the computer. To use an exec. tape from one machine on another is often asking for trouble.

We had a source who could copy an Allen Bradley tape to floppy but I don't know if that was the only brand they could work on.
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