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UG473 (v1.11) November 12, 2014
Block RAM Library Primitives
no longer allowed. The access to uninstantiated block RAM is prevented by disabling the
internal operation.
Block RAM Library Primitives
The 7 series FPGAs block RAM library primitives, RAMB18E1 and RAMB36E1, are the
basic building blocks for all block RAM configurations. Other block RAM primitives and
macros are based on these primitives. Some block RAM attributes can only be configured
using one of these primitives (for example, pipeline register, cascade). See the Block RAM
Attributes section.
The input and output data buses are represented by two buses for 9-bit width (8 + 1), 18-bit
width (16 + 2), and 36-bit width (32 + 4) configurations. The ninth bit associated with each
byte can store parity/error correction bits or serve as additional data bits. No specific
function is performed on the ninth bit. The separate bus for parity bits facilitates some
designs. However, other designs safely use a 9-bit, 18-bit, or 36-bit bus by merging the
regular data bus with the parity bus. Read/write and storage operations are identical for
all bits, including the parity bits.
Figure 1-9 illustrates all the I/O ports of the 36 Kb true dual-port block RAM primitive
(RAMB36). Table 1-6 lists these primitives.
X-Ref Target - Figure 1-9
Figure 1-9: Block RAM Port Signals (RAMB36E1)
DOPADOP
DOPBDOP
DIADI
DIPADIP
ADDRARDADDR
WEA
ENARDEN
RSTREGARSTREG
CLKARDCLK
DOADO
DOBDO
RSTRAMARSTRAM
REGCEAREGCE
DIBDI
DIPBDIP
ADDRBWRADDR
WEBWE
ENBWREN
RSTREGB
RSTRAMB
REGCEB
CLKBWRCLK
UG473_c1_09_052610
32
4
16
4
32
4
32
4
32
4
16
8
CASCADEOUTA CASCADEOUTB
CASCADEINA CASCADEINB
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