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AR# 2119

FPGA Configuration: Device seems to be in bypass mode and will not configure.

Description

KEYWORDS:

FPGA, Configuration, bypass, cclk, daisy chain, noise, ringing

URGENCY:

Standard

GENERAL PROBLEM DESCRIPTION:

Device(s) in daisy chain seems to be in bypass mode and will

not configure properly.

The device(s) having problem can be any where in the chain and

can be one or multiple devices within the chain. You may

noticed that configuration data going in at DIN is coming right

out from DOUT one cclk cycle later, indicating that the device

is already full when it has not been configured yet.

Solution

Using logic analyzer or scope, check the signal on cclk near

the device having problem. A noise or ringing on cclk may be

the cause of this problem. In order to reduce the

noise/ringing, try adding 30-50 shunt capacitor on the cclk

line.

Also, refer to Configuration Guideline Application note in the PFGA Databook for more debugging tips related to configuration problem.

AR# 2119
Date Created 08/21/2007
Last Updated 05/08/2014
Status Archive
Type General Article