Architecture
LatticeECP2/M Family Data Sheet
Lattice Semiconductor
sysMEM Memory
LatticeECP2/M devices contains a number of sysMEM Embedded Block RAM (EBR). The EBR consists of an 18-
Kbit RAM with dedicated input and output registers.
sysMEM Memory Block
The sysMEM block can implement single port, dual port or pseudo dual port memories. Each block can be used in
a variety of depths and widths as shown in Table 2-6. FIFOs can be implemented in sysMEM EBR blocks by imple-
menting support logic with PFUs. The EBR block facilitates parity checking by supporting an optional parity bit for
each data byte. EBR blocks provide byte-enable support for configurations with18-bit and 36-bit data widths.
Table 2-6. sysMEM Block Configurations
Memory Mode
Configurations
16,384 x 1
8,192 x 2
4,096 x 4
2,048 x 9
1,024 x 18
512 x 36
Single Port
16,384 x 1
8,192 x 2
4,096 x 4
2,048 x 9
1,024 x 18
True Dual Port
16,384 x 1
8,192 x 2
4,096 x 4
2,048 x 9
1,024 x 18
512 x 36
Pseudo Dual Port
Bus Size Matching
All of the multi-port memory modes support different widths on each of the ports. The RAM bits are mapped LSB
word 0 to MSB word 0, LSB word 1 to MSB word 1, and so on. Although the word size and number of words for
each port varies, this mapping scheme applies to each port.
RAM Initialization and ROM Operation
If desired, the contents of the RAM can be pre-loaded during device configuration. By preloading the RAM block
during the chip configuration cycle and disabling the write controls, the sysMEM block can also be utilized as a
ROM.
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
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.
EBR memory supports two forms of write behavior for single port or dual port operation:
1. Normal – Data on the output appears only during a 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.
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LATTICE [ LATTICE SEMICONDUCTOR ]
