FLEX8000 datasheet(21/61 Pages) ALTERA

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Altera Corporation

FLEX 8000 Programmable Logic Device Family Data Sheet

Figure 12. FLEX 8000 Column-to-IOE Connections

In addition to general-purpose I/O pins, FLEX 8000 devices have four

dedicated input pins. These dedicated inputs provide low-skew, device-

wide signal distribution, and are typically used for global clock, clear, and

preset control signals. The signals from the dedicated inputs are available

as control signals for all LABs and I/O elements in the device. The

dedicated inputs can also be used as general-purpose data inputs because

they can feed the local interconnect of each LAB in the device.

Signals enter the FLEX 8000 device either from the I/O pins that provide

general-purpose input capability or from the four dedicated inputs. The

IOEs are located at the ends of the row and column interconnect channels.

I/O pins can be used as input, output, or bidirectional pins. Each I/O pin

has a register that can be used either as an input register for external data

that requires fast setup times, or as an output register for data that

requires fast clock-to-output performance. The MAX+PLUS II Compiler

uses the programmable inversion option to automatically invert signals

from the row and column interconnect when appropriate.

The clock, clear, and output enable controls for the IOEs are provided by

a network of I/O control signals. These signals can be supplied by either

the dedicated input pins or by internal logic. The IOE control-signal paths

are designed to minimize the skew across the device. All control-signal

sources are buffered onto high-speed drivers that drive the signals around

the periphery of the device. This “peripheral bus” can be configured to

provide up to four output enable signals (10 in EPF81500A devices), and

up to two clock or clear signals. Figure 13 shows how two output enable

signals are shared with one clock and one clear signal.

IOE

Column Interconnect

Each IOE is

driven by an

8-to-1

multiplexer.

Each IOE can drive

up to two column

signals.

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