AR# 2841

FPGA Configuration: SSM - DONE doesn't go HIGH if CCLK starts Low.

Description

General Description:

In Slave Serial Mode Configuration of an xc4000XL device if the

CCLK starts out at a logic LOW, and is parked LOW after

configuration, the device may not configure. This was a known

problem with the xc3000 and xc4000 FPGA families, but was fixed

in the xc4000E family. However, some xc4000XL parts

exhibit this same problem.

Solution

Older FPGA familes had a maximum low time specification for

CCLK, `Tccl', however, this has not yet been characterized for

the xc4000XL. This has been fixed in the xc4000XLA devices

negating the characterization of a maximum Tccl.

Applications exhibiting this kind of behavior with xc4000XL

parts should be encouraged to invert the sense of the

configuration clock.

AR# 2841
Date 05/07/2014
Status Archive
Type General Article