ATF1500ABV/L

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ATF1500ABV Macrocell

ATF1500ABV Macrocell

The ATF1500ABV macrocell is flexible enough to support

highly complex logic functions operating at high speed. The

macrocell consists of five sections: product terms and prod-

uct term select multiplexer; OR/XOR/CASCADE logic; a flip

flop; output select and enable; and logic array inputs.

Product Terms and Select Mux

Each ATF1500ABV macrocell has five product terms. Each

product term receives as its inputs all signals from both the

global bus and regional bus.

The product term select multiplexer (PTMUX) allocates the

five product terms as needed to the macrocell logic gates

and control signals. The PTMUX programming is deter-

mined by the design compiler, which selects the optimum

macrocell configuration.

OR/XOR/CASCADE Logic

The ATF1500ABV macrocell's OR/XOR/CASCADE logic

structure is designed to efficiently support all types of logic.

Within a single macrocell, all the product terms can be

routed to the OR gate, creating a five input AND/OR sum

term. With the addition of the CASIN from neighboring

macrocells, this can be expanded to as many as 40 product

terms with a very small additional delay.

The macrocell's XOR gate allows efficient implementation

of compare and arithmetic functions. One input to the XOR

comes from the OR sum term. The other XOR input can be

a product term or a fixed high or low level. For combinato-

rial outputs, the fixed level input allows output polarity

selection. For registered functions, the fixed levels allow De

Morgan minimization of the product terms. The XOR gate is

also used to emulate JK type flip flops.

Flip Flop

The ATF1500ABV’s flip flop has very flexible data and con-

trol functions. The data input can come from either the XOR

gate or from a separate product term. Selecting the sepa-

rate product term allows creation of a buried registered

feedback within a combinatorial output macrocell.

In addition to D, T, JK and SR operation, the flip flop can

also be configured as a flow-through latch. In this mode,