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Altera_Forum's avatar
Altera_Forum
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17 years ago

JTAG pin 6

Hi,

I design a board with cyclone II.

I employ JTAG for configuration, signaltap ...

My question is : What does pin n°6 of jtag be connected to ?

In Cyclone handbook, it is just a note that says

--- Quote Start ---

Pin 6 of the header is a VIO reference voltage for the MasterBlaster output driver. VIO should match the device’s

VCCIO. Refer to the MasterBlaster Serial/USB Communications Cable Data Sheet for this value. In the ByteBlasterMV

cable, this pin is a no connect. in the usb-blaster and byteblaster ii cable, this pin is connected to nce when it is

used for as programming, otherwise it is a no connect.

--- Quote End ---

Should I leave this pin unconnected ? or connected to 3.3V from the board ?

On NiosII EP2C35 dev kit, it is connected to vccio through 1kOhm resistor.

8 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    Thanks,

    SO, no need to connect to Vccio (3.3V)

    also, Could it be connected to Vccio without damage ? I think yes (I have this on older boards)
  • Altera_Forum's avatar
    Altera_Forum
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    17 years ago

    The no connect doesn't imply, that the pin is unconnected at the USB Blaster. Cause this AS programming pin has no separate OE, it is also driven in JTAG mode, but to a high level. Thus you shouldn't have problems when shorting it to pin 4 (VCC) at the board.

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    I have burnt 2 USB Blaster (same symptoms) with card in which JTAG pin 4 and 6 are connected to VCC. I notice that those 2 USB Blaster were > 1 year old and many, many, many operations.

    On Altera's kits,

    JTAG 6 goes to VCC through 1 kOhm

    JTAG 4 goes to VCCA or VccIO through 1 kOhm

    I will have a look on Altera literature to figure out.
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    --- Quote Start ---

    I have burnt 2 USB Blaster (same symptoms) with card in which JTAG pin 4 and 6are connected to VCC

    --- Quote End ---

    The pin 6 connection involves an additional risk when connecting or disconnecting the USB interface while the USB Blaster is powered by the target board, because the JTAG drivers apparently aren't hot-plug proof. I didn't consider this problem in my above statement.

    --- Quote Start ---

    JTAG 4 goes to VCCA or VccIO through 1 kOhm

    --- Quote End ---

    No it's usually connected without a series resistor. Because the pin supplies the JTAG drivers in the USB Blaster, a series resistor must be at least low resistance to allow USB Blaster operation.
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    To resume,

    On cyclone II, (http://www.altera.com/literature/hb/cyc2/cyc2_cii5v1_06.pdf figure 13-25)

    JTAG pin 1 connected to FPGA TCK with 1k pulled down.....JTAG pin 2 connected to GND

    JTAG pin 3 connected to FPGA TDO..................................jtag pin 4 directly connected to vccio.

    JTAG pin 5 connected to FPGA TMS with 1k Pulled UP.........jtag pin 6 no connect (for usb blaster and byteblaster ii).

    JTAG pin 7 No Connect....................................................JTAG pin 8 No Connect.

    JTAG pin 9 to FPGA TDI with 1k Pulled UP.........................JTAG pin 10 to GND.

    Is it right ?

    250$ burnt for just one pin :eek: :d
  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    Replacing the JTAG drivers should be sufficient to repair the parts.