Answers Database
XC4000XL/XV: XV vs XL Architectural Differences
Record #3283
Product Family: Hardware
Product Line: 4000
Product Part: 4000XV
Problem Title:
XC4000XL/XV: XV vs XL Architectural Differences
Problem Description:
FCLK: Similar to the EX/XL architecture, the XV devices have an FCLK along the left
and right edge of the device. The main difference lies in its implementation. In the XL
devices, one of the two paths I1, I2 in the IOB is used for the FCLK. However, in the
XV devices the FCLK path is independent of I1 and I2. The FCLK path is programmed
in the bitstream such that the I1, I2 and FCLK paths are mutually exclusive. This is
done by using an unused combination of the 2 bits used to program the MUXES in the I1,I2
paths to program the FCLK path. This feature has been added primarily for speed.
5V PCI in the IOBs: From a circuit viewpoint, a 5V PCI drive in the IOBs essentially
means added drive in the IOBs. This is accomplished by increasing the drive of the IOB
by an additional parallel buffer controlled by a configuration bit. This implies a
bitstream change. For all IOBs except the center IOB on the left side this configuration
bit is an unused bit from the XL bitstream. For the center IOB on the left side, this
bit happens to be the charge-pump control bit. Since the charge pump is not being used
in either the XL or the XV this bit does not pose any new functionality in the
XV. Buffered TBUF long lines: In the XL architecture, the TBUF Horizontal Long Line
has 5 pips per tile that allow for the TBUF HLL to drive inputs. These pips are
unbuffered in the XL architecture. In the XV architecture, these pips are buffered from
the TBUF HLL by a single buffer. The buffer drives a segment with these 5 pips as
shown below.
Solution 1:
End of Record #3283 - Last Modified: 01/16/98 00:48 |
