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Altera_Forum's avatar
Altera_Forum
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15 years ago

beginning with CPLD's

hello.

I want to start with CPLD's like the title said, but i have absolutely 0 experience with them.

I ordered an Altera USB blaster and i am designing a CPLD board.

I am going to start with an EPM3064, i don't have plans to make something big so that device should be big enough for a while.

Its also in a hand solder-able TQFP44 package.

Now for the questions:

For programming, my idea was to simply put a 10 pins header on the board, connect it, (TDO from jtag conector to TDO on the device ect ect) and done.

Is that enough?

Are all VCC/GND pins internally connected or should i connect them on the board?

If i want to connect a crystal, do i need a normal 2 pins crystal or a crystal oscillator that requires a 5 or 3.3V power supply?

I would like it to be a small single layer board, i hope thats fairly possible :)

Rik

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    The JTAG interface should have a TCK pull-down and TMS/TDI pull-up resistors. All supply pins have to be connected, bypass capacitors are required in addition. The clock input should be connected to a 3.3V crystal oscillator.

    Feasibility of a single layer board depends on what you are connecting to the CPLD inputs. It's difficult anyway. Insufficient ground connection can e.g. cause double clocking through ringing clock signals or failure of the JTAG interface.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    15 years ago

    Hmm to bad, i was hoping to fit an CPLD, jtag header and a crystal on a MBED size board.

    (i would link an image to an MBED here but i cant, need 5 posts first, if you dont know it, google it :D)

    But making that single layer is impossible it seems

    I'll go for an arduino sized PCB then and imma use my awesome dual layer technique.

    Making 2 single layer PCB's and glue them together as i can only etch single layers at home.

    Don't worry, if the prototype works I'll make some professional.

    For the decoupling caps, is 1 cap per side (4 total) enough, 100nF caps?

    Or do i need to add tantalum caps to?

    Little question about the crystal, as the I/O pins are 5V tolerant, can i use a normal 5V crystal?

    I am planning on just making a schematic with logic blocks and upload it in the CPLD.

    So connect the crystal to 2 random I/O ports and then make a multiplier/divider and just select the 2 I/O pins as input for them?

    Or do i need to connect the crystal to specified pins?

    Thanks for the help,

    Rik