Xilinx virtex-5 fpga

164 www.xilinx.com Virtex-5 FPGA User Guide
UG190 (v5.0) June 19, 2009
Chapter 4: Block RAM
Block RAM and FIFO ECC Attributes
In addition to the built-in registers in the decode and correct logic, the RAMB36SDP
primitive allows the use of optional pipeline registers controlled by the DO_REG attribute
to produce higher performance with one additional latency. Table 4-23 and Table 4-24 list
the block RAM and FIFO ECC attributes.
Table 4-23: Block RAM (RAMB36SDP) Attributes
Attribute Name Type Values Default Notes
EN_ECC_WRITE Boolean TRUE, FALSE FALSE Set to TRUE to enable ECC encoder.
EN_ECC_READ Boolean TRUE, FALSE FALSE Set to TRUE to enable ECC decoder.
DO_REG 1-bit Binary 0, 1 0 Enables register mode or latch mode.
Table 4-24: FIFO (FIFO36_72) Attributes
Attribute Name Type Values Default Notes
EN_ECC_WRITE Boolean TRUE, FALSE FALSE Both attributes must be set to TRUE to
enable ECC functionality in a
FIFO36_72.
EN_ECC_READ
Boolean TRUE, FALSE FALSE
DO_REG
1-bit
Binary
0, 1 1
Enables register mode or latch mode. See
Table 4-17 for details on multirate and
synchronous FIFOs.
EN_SYN
Boolean TRUE, FALSE FALSE
When set to TRUE, ties WRCLK and
RDCLK together.
When set to TRUE, FWFT must be
FALSE.
When set to FALSE, DO_REG must be 1.
ALMOST_EMPTY_OFFSET
9-bit
Hex
See Table 4-19 See Table 4-19
Setting determines the difference
between EMPTY and ALMOST_EMPTY
conditions. Must be set using
hexadecimal notation.
ALMOST_FULL_OFFSET
9-bit
Hex
See Table 4-19 See Table 4-19
Setting determines the difference
between FULL and ALMOST_FULL
conditions. Must be set using
hexadecimal notation.
FIRST_WORD_FALL_THROUGH
Boolean TRUE, FALSE FALSE
When set to TRUE, the first word written
into the empty FIFO36_72 appears at the
FIFO36_72 output without RDEN
asserted.