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Xilinx Constraints Guide

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Chapter 4: <strong>Xilinx</strong> <strong>Constraints</strong><br />

Standard Block Delay Symbols for Path Tracing<br />

Delay Symbol Name Path Type Default<br />

reg_sr_o Asynchronous Set/Reset to output<br />

propagation delay<br />

reg_sr_r Asynchronous Set/Reset to recovery<br />

path<br />

reg_sr_clk Synchronous Set/Reset to clock setup<br />

and hold checks<br />

Disabled<br />

Disabled for Virtex®-5 and earlier<br />

architectures<br />

Enabled for Virtex-6 and Spartan®-6<br />

architectures<br />

Enabled<br />

lat_d_q Data to output transparent latch delay Disabled<br />

lat_ce_q Clock Enable to output transparent<br />

latch delay<br />

ram_we_o RAM write enable to output<br />

propagation delay<br />

Disabled<br />

Enabled<br />

io_pad_i IO pad to input propagation delay Enabled<br />

io_t_pad IO tristate to pad propagation delay Enabled<br />

io_o_1 IO output to input propagation delay.<br />

Disabled for tristated IOBs<br />

Enabled<br />

io_o_pad IO output to pad propagation delay Enabled<br />

PCF Syntax<br />

ENABLE=delay_symbol_name ;<br />

TIMEGRP name ENABLE=delay_symbol_name ;<br />

<strong>Constraints</strong> <strong>Guide</strong><br />

110 www.xilinx.com UG625 (v. 13.2) July 6, 2011

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