The following subsections describe IOB and CLB flip-flop initialization.
To set the initial value of Spartan/XL and XC4000E/L/EX/XV/XL IOB flip-flops at power-up, follow these instructions.
Set the IOB flip-flops to power up either High or Low by attaching the appropriate INIT property (INIT=1 or INIT=0) to each IOB flip-flop in your schematic. The default value of INIT is 0. When you activate the global reset signal (GSR) during simulation, the IOB flip-flops initialize to this assigned value.
To set the initial value of Spartan/XL and XC4000E/L/EX/XV/XL CLB flip-flops at power-up, follow these instructions.
To get a flip-flop which initializes to 0 at power-up, select a flip-flop macro or primitive with an asynchronous RESET input (FDCE, for example, has an asynchronous reset input called “CLR”).
To get a flip-flop which initializes to 1 at power-up, select a flip-flop macro or primitive with an asynchronous SET input (FDPE, for example, has an asynchronous preset pin called “PRE”).
