XC4VFX40-10FFG1152C Xilinx Inc, XC4VFX40-10FFG1152C Datasheet - Page 29

• Manufacturer Part Number: XC4VFX40-10FFG1152C
• Description: IC FPGA VIRTEX-4 FX 40K 1152FBGA
• Manufacturer: Xilinx Inc
• Series: Virtex™-4r

Specifications of XC4VFX40-10FFG1152C

• Number Of Logic Elements/cells: 41904
• Number Of Labs/clbs: 4656
• Total Ram Bits: 2654208
• Number Of I /o: 448
• Voltage - Supply: 1.14 V ~ 1.26 V
• Mounting Type: Surface Mount
• Operating Temperature: 0°C ~ 85°C
• Package / Case: 1152-BBGA, FCBGA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Number Of Gates: -

Virtex-4 FPGA User Guide
UG070 (v2.6) December 1, 2008
R
change, the output is kept Low until the other (“to-be-selected”) clock has transitioned
from High to Low. Then the new clock starts driving the output.The default configuration
for BUFGCTRL is falling edge sensitive and held at Low prior to the input switching.
BUFGCTRL can also be rising edge sensitive and held at High prior to the input switching.
In some applications the conditions previously described are not desirable. Asserting the
IGNORE pins bypasses the BUFGCTRL from detecting the conditions for switching
between two clock inputs. In other words, asserting IGNORE causes the mux to switch the
inputs at the instant the select pin changes. IGNORE0 causes the output to switch away
from the I0 input immediately when the select pin changes, while IGNORE1 causes the
output to switch away from the I1 input immediately when the select pin changes.
Selection of an input clock requires a “select” pair (S0 and CE0, or S1 and CE1) to be
asserted High. If either S or CE is not asserted High, the desired input is not selected. In
normal operation, both S and CE pairs (all four select lines) are not expected to be asserted
High simultaneously. Typically only one pin of a “select” pair is used as a select line, while
the other pin is tied High. The truth table is shown in
Table 1-4: Truth Table for Clock Resources
Although both S and CE are used to select a desired output, each one of these pins behaves
slightly different. When using CE to switch clocks, the change in clock selection can be
faster than when using S. Violation in setup/hold times of the CE pins causes a glitch at the
clock output. On the other hand, using the S pins allows the user to switch between the two
clock inputs without regard to setup/hold times. It does not result in a glitch. See the
discussion of “BUFGMUX_VIRTEX4”. The CE pin is designed to allow backward
compatibility from Virtex-II and Virtex-II Pro FPGAs.
Notes:
1. Old input refers to the valid input clock before this state is achieved.
2. For all other states, the output becomes the value of INIT_OUT and does not toggle.
CE0
X
1
1
0
1
S0
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X
1
1
0
1
CE1
X
0
1
1
1
Table
1-4.
Global Clocking Resources
S1
X
0
1
1
1
Old Input
O
I0
I0
I1
I1
(1)
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