Architecture
LatticeECP/EC Family Data Sheet
Lattice Semiconductor
Memory Cascading
Larger and deeper blocks of RAM can be created using EBR sysMEM Blocks. Typically, the Lattice design tools
cascade memory transparently, based on specific design inputs.
Single, Dual and Pseudo-Dual Port Modes
Figure 2-15 shows the four basic memory configurations and their input/output names. In all the sysMEM RAM
modes the input data and address for the ports are registered at the input of the memory array. The output data of
the memory is optionally registered at the output.
Figure 2-15. sysMEM EBR Primitives
ADA[12:0]
DIA[17:0]
CLKA
CEA
RSTA
WEA
CSA[2:0]
DOA[17:0]
ADB[12:0]
DIB[17:0]
CEB
CLKB
RSTB
WEB
CSB[2:0]
DOB[17:0]
AD[12:0]
DI[35:0]
CLK
DO[35:0]
CE
EBR
EBR
RST
WE
CS[2:0]
True Dual Port RAM
Single Port RAM
ADW[12:0]
DI[35:0]
CLKW
CEW
ADR[12:0]
DO[35:0]
AD[12:0]
CLK
DO[35:0]
CE
EBR
ROM
EBR
WE
RST
CS[2:0]
CER
RST
CS[2:0]
CLKR
Pseudo-Dual Port RAM
The EBR memory supports three forms of write behavior for single port or dual port operation:
1. Normal – data on the output appears only during read cycle. During a write cycle, the data (at the current
address) does not appear on the output. This mode is supported for all data widths.
2. Write Through – a copy of the input data appears at the output of the same port during a write cycle. This
mode is supported for all data widths.
3. Read-Before-Write – when new data is being written, the old content of the address appears at the output.
This mode is supported for x9, x18 and x36 data widths.
Memory Core Reset
The memory array in the EBR utilizes latches at the A and B output ports. These latches can be reset asynchro-
nously or synchronously. RSTA and RSTB are local signals, which reset the output latches associated with Port A
and Port B, respectively. The Global Reset (GSRN) signal resets both ports. The output data latches and associ-
ated resets for both ports are as shown in Figure 2-16.
2-13
LATTICE [ LATTICE SEMICONDUCTOR ]
