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Zvi's avatar
Zvi
Icon for New Contributor rankNew Contributor
1 month ago

JTAG pins order for USB Blaster III - 1.27" header

USB Blaster III header has shrined in size relatively to the previous JTAG cables.

I see that in addition, pinout order has changed(according to USB Blaster III user guide).

So, if I want to place on a new board that I'm developing a matching connector(pitch=1.27") for USB Blaster III (without using the adapter board from the KIT), then I have to use new pinout order: 1-VCC_TRGET, 2-TMS, 3-GND, 4-TCK, 6-TDO, 7-nTRST, 8-TDI, 9-GND, 10-nPROCRST.

This order is different then was used with previous JTAG cables.

I couldn't find any reference schematic(also of EVAL KITs) that supports this new JTAG order.

I will appreciate if anyone from the forum can confirm my observation.

If it's possible that someone can answer me with an existing working reference design with 1.27" connector, I will appreciate it more.

 

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1 Reply

  • FakhrulA_altera's avatar
    FakhrulA_altera
    Icon for Regular Contributor rankRegular Contributor
    1 month ago

    Hi Zvi,

    Yes. For a new board with the USB Blaster III 1.27 mm, 2 × 5 JTAG connector, use the USB Blaster III micro-header pinout, not the older 2.54 mm header order.

    For JTAG mode, the pinout is:

    Pin

    Signal

    1 - VCC_TARGET

    2 - TMS

    3 - GND

    4 - TCK

    5 - Not connected

    6 - TDO

    7 - Not connected

    8 - TDI

    9 - GND

    10 - nPROCRST
     

    So, pin 7 is not used for JTAG. It is used as nCS only in Active Serial mode.

    The 1.27 mm connector was introduced for a smaller cable interface. The included adapter board maps this new pinout to the older 2.54 mm header, which is why the signal order differs from older cables.


    For a direct connection, use a keyed 1.27 mm, 2 × 5 male header on the target board and follow the pin numbering shown in the USB Blaster III User Guide. At this time, the adapter-board mapping in the user guide is the available reference for this interface.

    USB Blaster III FPGA Development Cable User Guide

    Regards,
    Fakhrul