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Altera_Forum's avatar
Altera_Forum
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13 years ago

why usb blaster need be set a max3378 （Level conversion chip）

i have seen the altera usb blaster ，there is nothing Level conversion IC ，but others always said that it should be a Level conversion ic in the usb blaster to fit the different Level of the target board...

could you tell me why？

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  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    There's two different situations to consider;

    1) A USB-Blaster cable

    This type of USB-Blaster gets plugged into a target board via the 10-pin JTAG header. The VCC_TARGET pin on this header powers a dual-supply buffer inside the programmer so that the logic levels driven onto the JTAG pins are appropriate for the target board.

    2) On-board USB-Blaster

    When the USB-Blaster is included on a PCB, there is no need for a level translator, since the designer of the board will ensure that the USB-Blaster JTAG logic levels (typically from a MAX series CPLD) are appropriate for the JTAG device attached to it.

    If you were to use an on-board USB-Blaster schematic as the reference design for building a USB-Blaster cable, then you would need to *add* the level translator to your design.

    Cheers,

    Dave