ISA TR50.02, PARTS 3&4

Introduction

Incomprehensibility

A long story of incomprehensibility has followed (and often alsopreceded) the ISA Fieldbus Data Link Layer (DLL) documents. That isdue to several reasons: some real ones, others only imagined butrepetitively suggested and spread around by some of the people whodid not agree with the proposal.

Standard style

First of all, the fear of compelling something relevant only tothe implementation domain always pushes standard documents not todescribe “why” or “how” but just “what” to do.

That, in this particular case of fieldbus, made things evenworse than usual because of the existing experiences and approachesof many experts being radically different; it led to real problems(and it eased many imagined ones) in mutual understanding.

Features variety

Due to the differences between the existing fieldbus approaches,the technical and diplomatic need of merging them has always beenthe key issue of all the ISA DLL efforts and has so increased thevariety of features and the complexity of the structure within sucha document that tries to harmonize them all.

Many updates

Then, the long path followed in order to chisel a proposal thatcould be really agreed by all the different existing approaches hascaused the need to frequently update, partially re-write, ordelete, or add many parts of the ISA Fieldbus DLL drafts alongseveral years.

And this, of course, did not give the documents the same clearstructure as an immediate paper would have had.

Effort to understand

Finally, we have to remind how only “if” and “when” we reallywant to implement something, then we make the effort to understandit. When we already have an existing, even if not universal,alternative why should we make such an effort?

Edition:

00

Published:

04/15/2000

Number of Pages:

126

File Size:

1 file , 3.6 MB