Xilinx virtex-5 fpga User Manual

180 www.xilinx.com Virtex-5 FPGA User Guide
UG190 (v5.0) June 19, 2009
Chapter 5: Configurable Logic Blocks (CLBs)
The initial state after configuration or global initial state is defined by separate INIT0 and
INIT1 attributes. By default, setting the SRLOW attribute sets INIT0, and setting the
SRHIGH attribute sets INIT1. Virtex-5 devices can set INIT0 and INIT1 independent of
SRHIGH and SRLOW.
The configuration options for the set and reset functionality of a register or a latch are as
follows:
• No set or reset
• Synchronous set
• Synchronous reset
• Synchronous set and reset
• Asynchronous set (preset)
• Asynchronous reset (clear)
• Asynchronous set and reset (preset and clear)
Distributed RAM and Memory (Available in SLICEM only)
Multiple LUTs in a SLICEM can be combined in various ways to store larger amount of
data.
The function generators (LUTs) in SLICEMs can be implemented as a synchronous RAM
resource called a distributed RAM element. RAM elements are configurable within a
SLICEM to implement the following:
• Single-Port 32 x 1-bit RAM
• Dual-Port 32 x 1-bit RAM
• Quad-Port 32 x 2-bit RAM
• Simple Dual-Port 32 x 6-bit RAM
• Single-Port 64 x 1-bit RAM
• Dual-Port 64 x 1-bit RAM
• Quad-Port 64 x 1-bit RAM
• Simple Dual-Port 64 x 3-bit RAM
• Single-Port 128 x 1-bit RAM
• Dual-Port 128 x 1-bit RAM
• Single-Port 256 x 1-bit RAM
Distributed RAM modules are synchronous (write) resources. A synchronous read can be
implemented with a storage element or a flip-flop in the same slice. By placing this flip-
flop, the distributed RAM performance is improved by decreasing the delay into the clock-
to-out value of the flip-flop. However, an additional clock latency is added. The distributed
elements share the same clock input. For a write operation, the Write Enable (WE) input,
driven by either the CE or WE pin of a SLICEM, must be set High.

Xilinx virtex-5 fpga Specifications

General

Brand	Xilinx
Model	virtex-5 fpga
Category	Computer Hardware
Language	English