ECP2 datasheet(22/386 Pages) LATTICE

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Architecture

Lattice Semiconductor

LatticeECP2/M Family Data Sheet

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

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:

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.

Memory Mode

Conﬁgurations

Single Port

16,384 x 1

8,192 x 2

4,096 x 4

2,048 x 9

1,024 x 18

512 x 36

True Dual Port

16,384 x 1

8,192 x 2

4,096 x 4

2,048 x 9

1,024 x 18

Pseudo 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

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