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ATF1504ASV(L)
1409H–PLD–09/02
OR/XOR/CASCADE Logic The ATF1504ASV(L)’s logic structure is designedtoefficiently support all types of logic.
Within a single macrocell, all the product terms can be routedtothe OR gate,creating a
5-input AND/OR sum term. With the addition of the CASIN from neighboring macrocells,
this can beexpandedtoasmanyas40 product terms with little additional delay.
The macrocell’sXOR gate allows efficient implementation of compare and arithmetic
functions. One input to the XOR comesfromthe OR sum term. The otherXOR input can
be a product term or a fixed high- or low-level. For combinatorial outputs, the fixedlevel
input allows polarity selection. For registered functions, the fixedlevels allow DeMorgan
minimization of product terms. The XOR gate is also usedtoemulate T- and JK-type
flip-flops.
Flip-flop The ATF1504ASV(L)’s flip-flop has very flexible data and control functions. The data
input can come from eitherthe XOR gate,fromaseparate product term or directly from
the I/Opin. Selecting the separate product term allows creation of a buriedregistered
feedback within a combinatorial output macrocell. (This feature is automatically imple-
mentedbythe fitter software). In addition to D,T,JKandSR operation, the flip-flop can
also be configured as a flow-through latch. In this mode, data passes through whenthe
clock is high and is latchedwhenthe clock is low.
The clock itself can eitherbe one of the Global CLK Signal (GCK[0 : 2]) or an individual
product term. The flip-flop changesstate on the clock’s rising edge. Whenthe GCK sig-
nal is usedasthe clock, one of the macrocell product terms can be selectedasaclock
enable. Whenthe clock enable function is active and theenable signal (product term) is
low, all clock edgesare ignored. The flip-flop’s asynchronous resetsignal(AR)canbe
eitherthe Global Clear (GCLEAR), a product term, or always off. AR canalsobe a logic
OR of GCLEAR with a product term. The asynchronous preset(AP)canbe aproduct
term or always off.
Extra Feedback The ATF1504ASV(L)macrocell output can be selectedasregistered or combinatorial.
Theextra buriedfeedback signal can beeither combinatorial or a registered signal
regardless of whetherthe output is combinatorial or registered. (This enhancement
function is automatically implementedbythe fittersoftware.)Feedback of a buried
combinatorial output allows the creation of a second latch within a macrocell.
I/O Control The output enable multiplexer(MOE)controlsthe output enable signal. Each I/Ocanbe
individually configured as an input, output or for bi-directional operation. The output
enable for each macrocell can be selectedfromthe true or compliment of the two output
enable pins, a subsetofthe I/O pins, or a subsetofthe I/Omacrocells. This selection is
automatically done by the fitter software whenthe I/Oisconfigured as an input, all mac-
rocell resourcesare still available, including the buriedfeedback, expander and cascade
logic.
Global Bus/Switch Matrix The global bus contains all input and I/O pin signals as well as the buriedfeedback sig-
nal from all 64 macrocells. The switch matrix in each logic block receivesasitsinputsall
signals from the global bus. Under software control, up to 40 of these signals can be
selected as inputs to the logic block.
Foldback Bus Each macrocell also generates a foldback product term. This signal goestothe regional
bus and is available to four macrocells. The foldback is an inverse polarity of one of the
macrocell’sproductterms. The four foldback terms in each region allow generation of
high fan-in sum terms (up to nine product terms) with little additional delay.
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