{"id":490,"date":"2013-05-28T10:37:08","date_gmt":"2013-05-28T18:37:08","guid":{"rendered":"https:\/\/formidableengineeringconsultants.com\/?p=490"},"modified":"2013-12-09T09:46:39","modified_gmt":"2013-12-09T17:46:39","slug":"its-old-its-new-its-too-complicated-its-much-improved","status":"publish","type":"post","link":"https:\/\/formidableengineeringconsultants.com\/?p=490","title":{"rendered":"It’s Old…It’s New…It’s Too Complicated…It’s Much Improved…"},"content":{"rendered":"

\"IEEE-1149-1-jtag-picture\"<\/a>That venerable electronic test standard IEEE Std 1149.1<\/a> (also known as JTAG; also known as Boundary-Scan; also known as Dot 1) has just been freshened up.\u00a0 This is no ordinary freshening.\u00a0 The standard, last revisited in 2001, is long overdue for some clarification and enhancement.\u00a0 It’s been a long time coming and now…it’s here.\u00a0 While the guts remain the same and in good shape, some very interesting options and improvements have been added.\u00a0 The improvements are intended to provide support for testing and verification of the more complex devices currently available and to acknowledge the more sophisticated test algorithms and capabilities afforded by the latest hardware.\u00a0 There is an attempt, as well, (perhaps though, only as well as one can do this sort of thing) to anticipate future capabilities and requirements and to provide a framework within which such capabilities and requirements can be supported.\u00a0 Of course, since the bulk of the changes are optional their value will only be realized if the end-user community embraces them.<\/p>\n

There are only some minor clarifications or relaxations to the rules that are already established. For the most part, components currently compliant with the previous version of this standard will remain compliant with this one. There is but one “inside baseball” sort of exception.\u00a0 The long denigrated and deprecated BC_6 boundary-scan cell has finally been put to rest.\u00a0It is, with the 2013 version,\u00a0no longer supported or defined, so any component supplier who chose to utilize this boundary-scan cell – despite all warnings to contrary – must now provide their own BSDL package defining this BC_6 cell\u00a0if they upgrade to\u00a0using the STD_1149_1_2013 standard package for their BSDL definitions.<\/p>\n

While this is indeed\u00a0a major revision,\u00a0I must again emphasize that\u00a0all the new items introduced are optional.\u00a0 One of the largest changes\u00a0is in documentation capability incorporating\u00a0 the introduction of a new executable description language called Procedural Description Language<\/a> (PDL)\u00a0to document test procedures unique to a component.\u00a0 PDL, a\u00a0TCL<\/a>-like language,\u00a0was adopted from the work of the\u00a0IEEE Std P1687 working group<\/a>. 1687 is a proposed IEEE Standard for the access to and operation of embedded instruments (1687 is therefore also known as iJTAG or Instrument JTAG). The first iteration of the standard was based on use of the 1149.1 Test Access Port and Controller to provide the chip access\u2014and a set of modified 1149.1-type Test Data Registers to create an access network for embedded instruments. PDL was developed to describe access to and operation of these embedded instruments.<\/p>\n

Now, let’s look at the details.\u00a0 The major changes are as follows:<\/p>\n

In the standard body:<\/p>\n