Showing papers by "Xilinx published in 1986"

Microprocessor oriented configurable logic element

Abstract: A microprocessor controlled configurable logic circuit achieves versatility by including a configurable combinational logic element, a configurable storage circuit, a configurable status buffer, and a configurable output select logic. The input signals to the configurable combinational logic element are input signals to the configurable logic circuit and feedback signals from the storage circuit. The storage circuit may be configured to operate as a D flip-flop with or without set and reset inputs, or as an edge detector. In conjunction with the combinational logic element, the storage circuit may also operate as a stage of a shift register or counter. The output select logic selects output from among the output signals of the combinational logic element and the storage circuit. The configurable status buffer may be configured to provide status information on selected important internal signals of the configurable logic circuit. A microprocessor interface structure may access an array of these configurable logic circuits through the status buffer to read different internal output signals from different circuits in the array. Providing separate input and output to a microprocessor leaves the storage element free for other uses and does not require the logic provided by the logic elements.

TTL/CMOS compatible input buffer with Schmitt trigger

Abstract: A TTL/CMOS compatible input buffer circuit comprises a Schmitt trigger input buffer stage and a reference voltage generator. In the TTL mode, the reference voltage generator supplies a reference voltage having a level that forces the trigger point of the Schmitt trigger to a predetermined value. In the CMOS mode, the reference voltage generator is disabled and a voltage equal to the power supply voltage is provided to the Schmitt trigger. The input buffer circuit affords an enhanced input noise margin and minimizes DC power loss.

CMOS power-on reset circuit

Abstract: A CMOS power-on reset circuit furnishes a reset signal for bringing the components of a circuit to a defined initial state when the common supply voltage is turned on. The output signal of the reset circuit assumes a first constant value as soon as the supply voltage rises above the level required to turn on the pulldown transistor of an initializing inverter in the reset circuit. A delay circuit causes the output signal of the reset circuit to remain at the first constant value for a period of time sufficient to allow the components of the circuit to settle. The output signal of the reset circuit is then forced to a second constant value. The reset circuit is suitable for use with power supply voltages which rise very rapidly or with power supply voltages which rise very slowly (DC sweep).