Answers Database

XC4000XL/XV: XV vs XL Architectural Differences


Record #3283

Product Family:  Hardware

Product Line:  4000

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 l
eft
   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 progra
mmed
   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 i
n the I1,I2
   paths to program the FCLK path. This feature has been added primarily for spe
ed.


5V PCI in the IOBs: From a circuit viewpoint, a 5V PCI drive in the IOBs essenti
ally
   means added drive in the IOBs. This is accomplished by increasing the drive o
f the IOB
   by an additional parallel buffer controlled by a configuration bit. This impl
ies a
   bitstream change. For all IOBs except the center IOB on the left side this co
nfiguration
   bit is an unused bit from the XL bitstream. For the center IOB on the left si
de, this

   bit happens to be the charge-pump control bit. Since the charge pump is not b
eing used
   in either the XL or the XV this bit does not pose any new functionality in th
e
   XV. Buffered TBUF long lines: In the XL architecture, the TBUF Horizontal Lon
g Line
   has 5 pips per tile that allow for the TBUF HLL to drive inputs. These pips a
re
   unbuffered in the XL architecture. In the XV architecture, these pips are buf
fered from
   the TBUF HLL by a single buffer. The buffer drives a segment with these 5 pip
s as
   shown below.


Solution 1:





End of Record #3283