Answers Database
4000E/EX: Can the BUFGLS, BUFGE, and BUFFCLK (4000X) and BUFGP and BUFGS (4000E) be driven with Internal Logic?
Record #1795
Product Family: Hardware
Product Line: 4000EX
Product Part: 4000EX
Problem Title:
4000E/EX: Can the BUFGLS, BUFGE, and BUFFCLK (4000X) and BUFGP and BUFGS (4000E) be driven
with Internal Logic?
Problem Description:
Urgency:
Standard
General Description:
For 4000X parts the BUFGLS (global low skew), BUFGE (global early) can all be
driven by either semi-dedicated pads or internal logic. The BUFFCLK (Fast clock)
may be driven by internal logic in a special way - see Resolution 3.
For 4000E parts the BUFGS (Secondary Global Buffers) can be driven by either semi-dedicated pads or
internal logic. While BUFGP (Promary Global Buffers) must be driven by the semi-dedicated pads.
Solution 1:
To source a BUFFCLK internally, you must driving signal must go through an OBUF and then the BUFFCLK
. This must be done because the BUFFCLK is only located on FCLK pins so placing the OBUF will allow
the mapper to push the signal out to the FCLK pin and then reroute it back in through the BUFFCLK.
Solution 2:
For a detailed description of each type of global clock buffer
in the XC4000X devices refer to pages 6-37 to 6-38 in the
1999 Xilinx Programmable Logic Data Book.
Solution 3:
For a detailed description of each type of global clock buffer
in the XC4000E devices refer to pages 6-35 in the 1999 Xilinx
Programmable Logic Data Book.
End of Record #1795 - Last Modified: 05/27/99 17:31 |
