XP2 datasheet(21/92 Pages) LATTICE

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2-18

Architecture

Lattice Semiconductor

LatticeXP2 Family Data Sheet

For further information on the sysMEM EBR block, please see TN1137, LatticeXP2 Memory Usage Guide.

EBR Asynchronous Reset

EBR asynchronous reset or GSR (if used) can only be applied if all clock enables are low for a clock cycle before the

reset is applied and released a clock cycle after the low-to-high transition of the reset signal, as shown in Figure 2-18.

The GSR input to the EBR is always asynchronous.

Figure 2-18. EBR Asynchronous Reset (Including GSR) Timing Diagram

If all clock enables remain enabled, the EBR asynchronous reset or GSR may only be applied and released after

the EBR read and write clock inputs are in a steady state condition for a minimum of 1/fMAX (EBR clock). The reset

release must adhere to the EBR synchronous reset setup time before the next active read or write clock edge.

If an EBR is pre-loaded during conﬁguration, the GSR input must be disabled or the release of the GSR during

device Wake Up must occur before the release of the device I/Os becoming active.

These instructions apply to all EBR RAM and ROM implementations.

Note that there are no reset restrictions if the EBR synchronous reset is used and the EBR GSR input is disabled.

sysDSP™ Block

The LatticeXP2 family provides a sysDSP block making it ideally suited for low cost, high performance Digital Sig-

nal Processing (DSP) applications. Typical functions used in these applications include Bit Correlators, Fast Fourier

Transform (FFT) functions, Finite Impulse Response (FIR) Filter, Reed-Solomon Encoder/Decoder, Turbo Encoder/

Decoder and Convolutional Encoder/Decoder. These complex signal processing functions use similar building

blocks such as multiply-adders and multiply-accumulators.

sysDSP Block Approach Compare to General DSP

Conventional general-purpose DSP chips typically contain one to four (Multiply and Accumulate) MAC units with

ﬁxed data-width multipliers; this leads to limited parallelism and limited throughput. Their throughput is increased by

higher clock speeds. The LatticeXP2 family, on the other hand, has many DSP blocks that support different data-

widths. This allows the designer to use highly parallel implementations of DSP functions. The designer can opti-

mize the DSP performance vs. area by choosing appropriate levels of parallelism. Figure 2-19 compares the fully

serial and the mixed parallel and serial implementations.

Reset

Clock

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