STRATIX 2 GX: CRU output frequency

Hi,

I'm using the STRATIX 2 GX and the ALT2GXB. So I will transmit and receive the data with 6250 Mbps. I programm the Stratix 2 GX with Quartus 8.0.

This are my configuration:

Protocol: Basic Double Width Mode

Operation Mode: Receiver and Transmitter

Channel: 1

Channel Width: 32 bit

Input Clock: 156.25 Mhz

Data rate: 6250 Mbps

If I compile my project, the "Analysis & Synthesis" part runs error free. But after that, the fitter gives an error.

This is the error message:

CRU output frequency 2500 Mhz (datarate 6250.0Mbps) of the receiver PLL of GX receiver channel atom "alt2gxb0:inst|alt2gxb:alt2gxb......" must be in the frequency range of 499.8 Mhz (datarate 1000Mbps) to 2127.7 Mhz (datarate 4255.3 Mbps).

Do someone know, how I can eliminate this error??

If I put the data rate to 3906.25 Mhz the project runs without a problem.

Because of this problem, I have read the handbook of the Stratix 2 GX again and I think on page 2-62 stands something about this problem. But it doesn't help me.

I hope someone in the forum can help me.

Many Thanks

yknarf