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JTAG compatible discrete IC's — Parallax Forums

JTAG compatible discrete IC's

mojorizingmojorizing Posts: 249
in General Discussion
I'm having a hard time finding what is available for JTAG compatible discrete logic IC's such as NAND Gates, Octal buffers, etc. I typically use Mouser and Digikey as suppliers and using their search functions isn't that helpful in finding these IC's. The searches come up with FPGA's, micrcontrollers, CPLD's, that sort of thing.

I've resorted to using http://bsdl.info/ to find if BSDL file exists for these components and then searching if they're available to purchase from a supplier - Smile backwards for sure....

I'm not looking for a JTAG compatible resistor network, it would be nice to know what is available for logic devices that I could add to a jtag enabled circuit!

Comments

  • Buck RogersBuck Rogers Posts: 2,185
    edited 2019-03-23 22:38
    Hello!
    The searches come up with those entries, because as of right now, today's date, that's all that the vendors have designed. And as it happens one vendor's line, TI, is decidedly complete on that score.

    It is in the nature of the logic behind the process that necessitates the reasons those vendors have. Now what are you building and perhaps I can help further?

    ---
    And this message is sponsored by the Rebel Alliance
  • jmgjmg Posts: 15,173
    mojorizing wrote: »
    I'm not looking for a JTAG compatible resistor network, it would be nice to know what is available for logic devices that I could add to a jtag enabled circuit!

    What exactly are you trying to do here ?

    mojorizing wrote: »
    I'm having a hard time finding what is available for JTAG compatible discrete logic IC's such as NAND Gates, Octal buffers, etc. I typically use Mouser and Digikey as suppliers and using their search functions isn't that helpful in finding these IC's. The searches come up with FPGA's, micrcontrollers, CPLD's, that sort of thing.
    NAND gates is quite an ask, as JTAG needs many pins to operate, so you will not find JTAG on low-pin count parts.

    TI did make some niche OCTAL parts in the series SN74BCT8xx, that you can find at Digikey, and those are 24 pin parts that are intended to add JTAG access to octal parts.
    You can still buy these, but they cost more than a CPLD.
  • mojorizingmojorizing Posts: 249
    I'd like to make a cheap JTAG Demo board to get familiar with the hardware and software that I've assembled. For hardware I have a clone of a Altera USB Blaster, I have JTAGLive from JTAG Technologies and Quartus II installed for software. Once I get comfortable with my setup, I need to use it to troubleshoot the motherboards on 2 old commercial Epilog Laser engravers. One motherboard works, the other doesn't....I got to keep the one that works working because Epilog doesn't provide schematics, and there are no spare motherboards. Up until now I've been scoping out the working motherboard for power, the fpga (Altera Flex EPF8820) boot up sequence, there's a MAX706 Supervisory circuit, and what I can see around the main processor (Motorola XPC821 (now known as a NXP MPC821)) and comparing it to the failed MB. This is all done while the boards are installed in the engravers, which makes it cumbersome.

    It looks like there's an issue with the XPC821 but without a schematic, I'm missing a lot (it's a 4 layer pcb). I would not perform a boundray scan, just a "watch" of the pin states of the XPC821 and go from there.

    Do you know of an inexpensive JTAG Demo board?
  • mojorizingmojorizing Posts: 249
    Both Engravers where downwind from a wood sander, and CNC mill that cut insulation foam that had aluminum foil on one surface. This was before the clean-up! Engravers were donated to a non-profit group and it's my job to get them working like new!
    Epliog.JPG
    4032 x 3024 - 3M
  • jmgjmg Posts: 15,173
    mojorizing wrote: »
    I'd like to make a cheap JTAG Demo board to get familiar with the hardware and software that I've assembled. For hardware I have a clone of a Altera USB Blaster, I have JTAGLive from JTAG Technologies and Quartus II installed for software. Once I get comfortable with my setup, I need to use it to troubleshoot the motherboards on 2 old commercial Epilog Laser engravers. One motherboard works, the other doesn't....I got to keep the one that works working because Epilog doesn't provide schematics, and there are no spare motherboards. Up until now I've been scoping out the working motherboard for power, the fpga (Altera Flex EPF8820) boot up sequence, there's a MAX706 Supervisory circuit, and what I can see around the main processor (Motorola XPC821 (now known as a NXP MPC821)) and comparing it to the failed MB. This is all done while the boards are installed in the engravers, which makes it cumbersome.

    Sounds like a lot of work.....
    mojorizing wrote: »
    It looks like there's an issue with the XPC821 but without a schematic, I'm missing a lot (it's a 4 layer pcb). I would not perform a boundray scan, just a "watch" of the pin states of the XPC821 and go from there.
    I'm not sure you can do that, as I think usually JTAG is used for bare board testing, programming etc, and holds the MCU in reset during activity.
    If you want a test system, you may be better to use something like a Prop board, as an 'engraver emulator', to allow you to probe these boards outside of their usual mounting.
    A Prop could do a mix of both Logic Analyzer and a signal emulator.

    How many connections would be needed to get minimal control action ? You might even be able to connect 1 prop to both boards, and play spot the difference.

  • yisiguroyisiguro Posts: 52
    I was looking for JTAG ready devices some weeks ago, and found Maxim DS4550, an I2C 9bit I/O expander. How about this ?
    https://www.maximintegrated.com/en/products/power/supervisors-voltage-monitors-sequencers/DS4550.html
  • Cluso99Cluso99 Posts: 18,069
    There are jtag buffers and latches 8+ bits wide. IIRC they are in the 74xx8xx family.
  • Buck RogersBuck Rogers Posts: 2,185
    edited 2019-03-27 14:04
    Cluso99 wrote: »
    There are jtag buffers and latches 8+ bits wide. IIRC they are in the 74xx8xx family.

    That they are. I have a bundle of them here, and also the parts used to basically assemble an entire controller mechanism for the technology.

    I have assembled simple a JTAG chain using a diagram I borrowed from the Wikipedia entry on the subject, and wired together two 74BCT8240A parts, and then basically talked to them using a Arduino (Sorry gang!) clone running a sketch which was normally used to reload stuff into a router's flash memory that got destroyed via the usual sloppy methods. Please see the attached for clews.
    654px-Jtag_chain.jpg
    314 x 120 - 10K
  • mojorizingmojorizing Posts: 249
    Mouser has the TI SN74BCT8244ADW and the Maxim DS4550E in single quantities, those are the ones I'LL order and make my JTAG demoboard.

    Thanks!
  • Buck RogersBuck Rogers Posts: 2,185
    mojorizing wrote: »
    Mouser has the TI SN74BCT8244ADW and the Maxim DS4550E in single quantities, those are the ones I'LL order and make my JTAG demoboard.

    Thanks!

    And you are very welcome. I've been trying to figure out how to confuse a Prop item to do the same thing as that Ard*** clone in an Altoids tin does do, that's what I run the sketch on. Naturally some bozo managed to tease an innocent Pi into doing the same thing, but I'm convinced that is a case of overkill.

    For example our hosts sell a Prop Mini and if I could safely get the programming as running on the typical QS board, for example, then that would be it. I mean what I had in mind might go on it. Of the basic Prop on a proto board one would work, I could include the resistors on it and something for the ribbon cable but i do not know. We are driving onto unknown terrain here, and you are the guide. Please keep us up to date.
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