I/O Mo d u le s
segments. The minimum horizontal segment length is the
width of a module-pair, and the maximum horizontal
segment length is the full length of the channel. Any segment
that spans more than one-third the row length is considered a
long horizontal segment. A typical channel is shown in
Figure 6. Non-dedicated horizontal routing tracks are used to
route signal nets. Dedicated routing tracks are used for the
global clock networks and for power and ground tie-off
tracks.
The I/O modules provide the interface between the device
pins and the logic array (shown in Figure 5). A variety of I/O
configurations, determined by a library macro selection, can
be implemented in the module (refer to the Macro Library
Guide for more information). I/O modules contain input and
output latches as well as a tri-state buffer. These features
allow the module to be configured for input, output, or
bi-directional pins.
Vertical Routing
EN
Other tracks run vertically through the module. Vertical
tracks are of three types: input, output, and long. Vertical
tracks are also divided into one or more segments. Each
segment in an input track is dedicated to the input of a
particular module. Each segment in an output track is
dedicated to the output of a particular module. Long segments
are uncommitted and can be assigned during routing. Each
output segment spans four channels (two above and two
below), except near the top and bottom of the array where
edge effects occur. An example of vertical routing tracks and
segments is shown in Figure 6.
Q
D
PAD
From Array
G/CLK*
Q
D
To Array
Segmented
Logic
G/CLK*
horizontal
Modules
routing
tracks
* Can be configured as a Latch or D Flip-Flop
(using C-module)
Figure 5 • I/O Module
Antifuses
I/O modules contain input and output latches for capturing
data prior to and/or from the device pins. In addition, the
Actel Designer Series software tools can build a D flip-flop
using a C-module in conjunction with the I/O latch to register
input and/or output signals. Actel’s Designer Series
development tools provide a design library of I/O macros
which can implement all I/O configurations supported by the
3200DX.
Vertical routing tracks
Figure 6 • Horizontal Routing Tracks and Segments
Antifuse Structures
R o u t in g S t r u c t u r e
An antifuse is a “normally open” structure as opposed to the
normally closed fuse structure used in PROMs or PALs. The
use of antifuses to implement a Programmable Logic Device
results in highly testable structures as well as efficient
programming algorithms. The structure is highly testable
because there are no pre-existing connections; therefore,
temporary connections can be made using pass transistors.
These temporary connections can isolate individual antifuses
to be programmed as well as isolate individual circuit
structures to be tested. This can be done both before and after
programming. For example, all metal tracks can be tested for
continuity and shorts between adjacent tracks, and the
functionality of all logic modules can be verified.
The 3200DX architecture uses Horizontal and Vertical
routing tracks to interconnect the various logic and I/O
modules. These routing tracks are metal interconnects that
may either be of continuous length or broken into pieces
called segments. Varying segment lengths allows the
interconnect of over 90% of design tracks to occur with only
two antifuse connections. Segments can be joined together at
the ends, using antifuses, to increase their lengths up to the
full length of the track. All interconnects can be
accomplished with a maximum of four antifuses.
Horizontal Routing
Horizontal channels are located between the rows of modules
and are composed of several routing tracks. The horizontal
routing tracks within the channel are divided into one or more
6