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3637B–PLD–1/08

ATF1504BE

Figure 1-4.

ATF1504BE Macrocell

1.1

Product Terms and Select Mux

Each ATF1504BE macrocell has five product terms. Each product term receives as its inputs all

signals from the switch matrix 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 configuration is determined by the design

compiler, which selects the optimum macrocell configuration.

1.2

OR/XOR/CASCADE Logic

The ATF1504BE’s logic structure is designed to efficiently support all types of logic. Within a sin-

gle macrocell, all the product terms can be routed to the OR gate, creating a 5-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 minimal 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 combinatorial outputs, the fixed level input allows polarity selec-

tion. For registered functions, the fixed levels allow DeMorgan minimization of product terms.

SCHMITT

TRIGGER

SSTL

BURIED FEEDBACK