MAX 3000A Programmable Logic Device Family Data Sheet
Each programmable register can be clocked in three different modes:
s
s
s
Global clock signal mode, which achieves the fastest clock-to-output
performance.
Global clock signal enabled by an active-high clock enable. A clock
enable is generated by a product term. This mode provides an enable
on each flipflop while still achieving the fast clock-to-output
performance of the global clock.
Array clock implemented with a product term. In this mode, the
flipflop can be clocked by signals from buried macrocells or I/O pins.
Two global clock signals are available in MAX 3000A devices. As shown
in
Figure 1,
these global clock signals can be the true or the complement
of either of the two global clock pins,
GCLK1
or
GCLK2.
Each register also supports asynchronous preset and clear functions. As
shown in
Figure 2,
the product-term select matrix allocates product terms
to control these operations. Although the product-term-driven preset and
clear from the register are active high, active-low control can be obtained
by inverting the signal within the logic array. In addition, each register
clear function can be individually driven by the active-low dedicated
global clear pin (GCLRn).
Expander Product Terms
Although most logic functions can be implemented with the five product
terms available in each macrocell, highly complex logic functions require
additional product terms. Another macrocell can be used to supply the
required logic resources. However, the MAX 3000A architecture also
offers both shareable and parallel expander product terms (“expanders”)
that provide additional product terms directly to any macrocell in the
same LAB. These expanders help ensure that logic is synthesized with the
fewest possible logic resources to obtain the fastest possible speed.
Shareable Expanders
Each LAB has 16 shareable expanders that can be viewed as a pool of
uncommitted single product terms (one from each macrocell) with
inverted outputs that feed back into the logic array. Each shareable
expander can be used and shared by any or all macrocells in the LAB to
build complex logic functions. A small delay (t
SEXP
) is incurred when
shareable expanders are used.
Figure 3
shows how shareable expanders
can feed multiple macrocells.
Altera Corporation
7
ETC [ ETC ]
