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Altera_Forum's avatar
Altera_Forum
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16 years ago

config pins and 1.2V

Hello,

I am currently designing a board with Cyclone III EP3C80 780 pin (I'm new in Altera world).

I have several banks with VCCIO 1.2V, but my concern is the configuration pins. I have an EPCS device, AS mode.

Do I have to use VCCIO = 3.3V on all banks that use config pins like ASDO, DEV_CLRn, nCONFIG, JTAG, etc. ?

At the moment, I have the following banks on 1.2V:

Bank 2, 3, 4 and 5. Others banks are 3.3V: 1, 6, 7 and 8.

Most of the config pins are on Bank 1 and 6 but I noticed DEV_CLRn on bank 5 and I would be annoyed to use 3.3V for this bank.

Please feel free to advice or make any remark.

Thank you for your answers.

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    16 years ago

    The configuration pins use the VccIO voltage of the bank they reside in, except the MSEL pins.

    You should use 3.3V VccIO for the bank that is connected to the EPCS, and for the others you can use any voltage. If you power the bank 5 at 1.2V, then the DEV_CLRn signal will also use the 1.2V standard (for inputs I believe that you can use different voltage levels than the bank VccIO, but there are some limits, described somewhere in the Cyclone III datasheet).
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    The most serious restriction regarding VCCIO of config pins is the requirement to provide a sufficient voltage to drive the AS memory chip. If you use original Altera devices, it's restricted to 3.3V. On input, a lower voltage IO standard can be overdriven without problems. The JTAG interface can use different IO standards, USB Blaster e.g. allows any IO standard down to 1.2V. DEV_CLRn is rarely used as a dedicated pin, I think.