XC4VFX12-10FFG668C Xilinx Inc, XC4VFX12-10FFG668C Datasheet - Page 152

• Manufacturer Part Number: XC4VFX12-10FFG668C
• Description: IC FPGA VIRTEX-4 FX 12K 668FCBGA
• Manufacturer: Xilinx Inc
• Series: Virtex™-4r

Specifications of XC4VFX12-10FFG668C

• Total Ram Bits: 663552
• Number Of Logic Elements/cells: 12312
• Number Of Labs/clbs: 1368
• Number Of I /o: 320
• Voltage - Supply: 1.14 V ~ 1.26 V
• Mounting Type: Surface Mount
• Operating Temperature: -40°C ~ 100°C
• Package / Case: 668-BBGA, FCBGA
• No. Of Logic Blocks: 12312
• No. Of Macrocells: 12312
• No. Of Speed Grades: 10
• No. Of I/o's: 320
• Clock Management: DCM
• I/o Supply Voltage: 3.45V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: HW-V4-ML403-UNI-G - EVALUATION PLATFORM VIRTEX-4HW-AFX-FF668-400 - BOARD DEV VIRTEX 4 FF668
• Number Of Gates: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 122-1591; XC4VFX12-10FFG668C

Chapter 4: Block RAM
152
ALMOSTEMPTY Flag
Read Error Flag
Full Flag
Write Error Flag
ALMOSTFULL Flag
The ALMOSTEMPTY flag is set when the FIFO contains the number of entries specified by
the ALMOST_EMPTY_OFFSET value (or fewer), warning the user to stop reading. The
ALMOSTEMPTY flag deasserts three clock cycles after the number of entries in the FIFO
becomes greater than the ALMOST_EMPTY_OFFSET value. It is synchronous to RDCLK.
Once the Empty flag has been asserted, any further read attempts will not increment the
read address pointer but will trigger the Read Error flag. The Read Error flag is deasserted
when Read Enable or Empty is deasserted Low. The Read Error flag is synchronous to
RDCLK.
The Full flag is synchronous with WRCLK, and is asserted one WRCLK after there are no
more available entries in the FIFO queue. Because of this latency, it is recommended to use
the ALMOST_FULL signal to stop further writing. When the FIFO is full, the write pointer
will be frozen. The Full flag is deasserted three write clock cycles after any read operation.
Once the Full flag has been asserted, any further write attempts will not increment the
write address pointer but will trigger the Write Error flag. The Write Error flag is
deasserted when Write Enable or Full is deasserted Low. This signal is synchronous to
WRCLK.
The ALMOSTFULL flag is set when the FIFO has the number of available empty spaces
specified by the ALMOST_FULL_OFFSET value or fewer. The ALMOSTFULL flag warns
the user to stop writing. It deasserts when the number of empty spaces in the FIFO is
greater than the ALMOST_FULL_OFFSET value, and is synchronous to WRCLK.
Table 4-11
Table 4-11: Clock Cycle Latency for Flag Assertion and Deassertion
Notes:
1. Depending on the time between read and write clock edges, the ALMOSTEMPTY and ALMOSTFULL
EMPTY
FULL
ALMOST EMPTY
ALMOST FULL
READ ERROR
WRITE ERROR
flags can deassert one cycle later.
Clock Cycle Latency
shows the number of clock cycles to assert or deassert each flag.
(1)
(1)
www.xilinx.com
Standard
0
1
1
1
0
0
Assertion
FWFT
0
1
1
1
0
0
UG070 (v2.6) December 1, 2008
Standard
Virtex-4 FPGA User Guide
3
3
3
3
0
0
Deassertion
FWFT
4
3
3
3
0
0
R