Programmable Logic - 2022.1 English

Versal ACAP Design Guide (UG1273)

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2022.1 English

The Versal ACAP programmable logic (PL) comprises configurable logic blocks (CLBs), internal memory, and DSP engines. Every CLB contains 64 flip-flops and 32 look-up tables (LUTs). Half of the CLB LUTs can be configured as a 64-bit RAM, as a 32-bit shift register (SRL32), or as two 16-bit shift registers (SRL16). In addition to the LUTs and flip-flops, the CLB contains the following:

  • Carry lookahead logic for implementing arithmetic functions or wide logic functions
  • Dedicated, internal connections to create fast LUT cascades without external routing

This enables a flexible carry logic structure that allows a carry chain to start at any bit in the chain. In addition to the distributed RAM (64-bit each) capability in the CLB, there are dedicated blocks for optimally building memory arrays in the design:

  • Accelerator RAM (4 MB) (available in some Versal devices only)
  • Block RAM (36 Kb each) where each port can be configured as 4Kx9, 2Kx18, 1Kx36, or 512x72 in simple dual-port mode
  • UltraRAM (288 Kb each) where each port can be configured as 32Kx9, 16Kx18, 8Kx36, or 4Kx72

Versal devices also include many low-power DSP Engines, combining high speed with small size while retaining system design flexibility. The DSP engines can be configured in various modes to better match the application needs:

  • 27×24-bit twos complement multiplier and a 58-bit accumulator
  • Three element vector/INT8 dot product
  • Complex 18bx18b multiplier
  • Single precision floating point

For more information on PL resources, see the Versal ACAP Configurable Logic Block Architecture Manual (AM005), Versal ACAP Memory Resources Architecture Manual (AM007), and Versal ACAP DSP Engine Architecture Manual (AM004).