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doubt regarding fpga I/O pin(urgent)

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Navya

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Hi,

We have used spartan 3 fpga(XC3S400) and leds are connected at the I/O pins.During the power on , all leds connected to I/O pins are glowing.
This is happening before program is loaded into the FPGA.Can anyone please explain what is happening inside fpga during power on to make the leds glow?

expecting early reply
 

IO status of fpga pin u cant predict on power up
,becouse fpga will take some time to arrage ur logic in harware , a pin called done is provided for this reson

after hardware arrange ment is done as per ur program done signal will become high
 

    Navya

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but these pins are showing 1.8v and the light is dim when compared to the led connected to power
 

supply voltage is 3.3v
before done signal..just after power up
 

the led connected to power
describe a little bit more about that power, please. How this LED is connected, to which power supply? and what power are selected and connected to the I/O bank power supply where this LED's are connected?

bis
 

leds are connected to the I/O pins of bank 5, 6 and 7 where 3.3 v is the supply
 

It sounds like your LEDs connect from the FPGA to ground, and the HSWAP_EN pin is grounded.

The Spartan-3 datasheet says, "A Low logic level on HSWAP_EN activates the pull-up resistors on all I/Os during configuration."
Therefore, current flows from VCCO (3.3V) through the pull-up resistor (a few kilo-ohms), through the LED, to ground.
 

    Navya

    Points: 2
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