EP20K200C Datasheet, PDF (37/90 Pages) Altera Corporation – Programmable Logic

I/O Structure
APEX 20KC Programmable Logic Device Data Sheet
Implementing Logic in ROM
In addition to implementing logic with product terms, the ESB can
implement logic functions when it is programmed with a read-only
pattern during configuration, creating a large LUT. With LUTs,
combinatorial functions are implemented by looking up the results, rather
than by computing them. This implementation of combinatorial functions
can be faster than using algorithms implemented in general logic, a
performance advantage that is further enhanced by the fast access times
of ESBs. The large capacity of ESBs enables designers to implement
complex functions in one logic level without the routing delays associated
with linked LEs or distributed RAM blocks. Parameterized functions such
as LPM functions can take advantage of the ESB automatically. Further,
the Quartus II software can implement portions of a design with ESBs
where appropriate.
Programmable Speed/Power Control
APEX 20KC ESBs offer a high-speed mode that supports very fast
operation on an ESB-by-ESB basis. When high speed is not required, this
feature can be turned off to reduce the ESB’s power dissipation by up to
50%. ESBs that run at low power incur a nominal timing delay adder. This
Turbo Bit^TM option is available for ESBs that implement product-term
logic or memory functions. An ESB that is not used will be powered down
so that it does not consume DC current.
Designers can program each ESB in the APEX 20KC device for either
high-speed or low-power operation. As a result, speed-critical paths in the
design can run at high speed, while the remaining paths operate at
reduced power.
The APEX 20KC IOE contains a bidirectional I/O buffer and a register
that can be used either as an input register for external data requiring fast
setup times or as an output register for data requiring fast clock-to-output
performance. IOEs can be used as input, output, or bidirectional pins.
Altera Corporation
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