Browse Prior Art Database

Techniques for Increasing ANR Data Link Transfer Rates

IP.com Disclosure Number: IPCOM000041703D
Original Publication Date: 1984-Mar-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Agnew, PW: AUTHOR [+5]

Abstract

IBM offers a program named Host Displaywriter Document Interchange (HDDI). HDDI allows a Displaywriter user to invoke two new functions. The first function transfers documents back and forth between the Displaywriters diskette and an attached VM/370 system's disk. The second function transforms documents back and forth between the Displaywriter's editable document form called OIIA L3 DCA, abbreviated here as L3, and an editable document form used on VM/370, called SCRIPT/VS. For example, the two functions allow a secretary to enter a document using a Displaywriter and then have a principal use a data processing terminal to edit it. The principal can then send it back to the Displaywriter for further editing, and so on.

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Techniques for Increasing ANR Data Link Transfer Rates

IBM offers a program named Host Displaywriter Document Interchange (HDDI). HDDI allows a Displaywriter user to invoke two new functions. The first function transfers documents back and forth between the Displaywriters diskette and an attached VM/370 system's disk. The second function transforms documents back and forth between the Displaywriter's editable document form called OIIA L3 DCA, abbreviated here as L3, and an editable document form used on VM/370, called SCRIPT/VS. For example, the two functions allow a secretary to enter a document using a Displaywriter and then have a principal use a data processing terminal to edit it. The principal can then send it back to the Displaywriter for further editing, and so on. This is possible because the document is kept in one or the other of the two editable forms, L3 or SCRIPT/VS. The present HDDI nibble algorithm, which is used when transferring documents, replaces each L3 document byte by two ANR link bytes. Each byte of data is split into two nibbles, each nibble ('O'X to 'F'X) is sent across the link as two safe bytes. The safe bytes used are 'FO'X to 'F9'X and 'C1'X to 'C6'X. This algorithm sends only 16 distinct values over the ANR link. This is wasteful. There are at least 80 "safe" values that can be sent over the ANR link. By "safe" values we mean ones that will be passed through any controller and not understood to be a control or significant byte by that controller. A huge majority of the bytes in an L3 document are letters and numbers, which are all safe. An even larger majority could be sent one-byte-per-byte if the most frequently used 80, or whatever, were sent as single bytes. Thus, one would reserve splitting of a byte into nibbles when that technique is needed. The following nibble algorithms are intended to significantly increase the ANR data transfer rate. NIBBLE ALGORITHM Partition the set of 256 byte values into three subsets (Example A): 1) safe values sent unchanged (except 1 reserved for step 2), 2) one safe value used as a "link escape character", meaning that the next two bytes sent represent one unsafe byte, and 3) unsafe values, each of which is sent as a link escape character, followed by two bytes from the set 0, 1, ''', 8, 9, A, '''F, which is a subset of subset
1. NIBBLE ALGORITHM B Partition the set of 256 byte values into three subsets (Example B): 1) safe values sent unchanged (except the 16 reserved for step 2) 16 safe values used in pairs to send the nibbles of an unsafe value and 3) unsafe values sent as pairs of the 16 selected safe values. NIBBLE ALGORITHM VARIANT Do not insist on sending values in the first subset unchanged. Instead, use the safe values to send the most frequently used values. (Examples A1 and B1.) There are two additional algorithms that may be used in conjunction with the stated algorithms above to increase the ANR Link Speed. Both of these algorithms decrease the number...