AR# 4006

描述

General Description:

How do I manually route a signal in EPIC?

解决方案

MANUAL ROUTING IN EPIC

First, you should always autoroute connections whenever possible. The EPIC

autorouter uses a delay-based algorithm to find the lowest delay path; this path

isn't always obvious to the user. The autorouter can also be used to route from a

route segment to a component pin to do "guided" autorouting.

The resources that can be manually routed are signal pins, local lines, and long

lines. A routing operation requires selecting at least two of these resources then

clicking the Route push button. Pinwires are routed by selecting their signal pins or

the pinwire itself.

The trick to manual routing is to select the resources that should be routed

together IN THE ORDER THAT THEY SHOULD BE CONNECTED. If you choose three

resources (for example, a signal pin, a local line, and a long line, in that order), the

manual router will attempt to connect the signal pin to the local line, and then the

local line to the long line. If no connection is possible, an error message will be

displayed in the history area. You can route through bidirectional PIPs or links in

either an upstream or downstream direction (i.e., towards or away from the driver

pin), but you cannot mix directions during a single route command.

Stub trimming is a global attribute which, when set to TRUE, draws only the

portions of the local and long resources which are visually relevant to the

propagation of the signal. This mode can be misleading since when zoomed in, a

local or long line resource can appear to be available when it is actually used.

Though stub trimming is set to TRUE by default in EPIC, we recommend setting it to

FALSE (in the Main Window Attributes dialog box) during manual routing.

Alternatively, you can see whether an apparently unused line really is unused by

selecting the line and then the Info or Attrib push button. NO SIGNAL indicates that

the line is unused; a net name associated with the line indicates that the line is

used. To turn Stub trimming on or off, go to Misc->Post Main Attrs.. and select or

deselect Stub Trimming.

Switch box connections are made by selecting the two local lines which are to be connected. To know the local lines to which another local line can connect, select the appropriate switch box pin. This will highlight the possible connections (some of these connections may not be possible because the lines are used). The switch box connection display does not interfere with manual routing and can be eliminated by selecting that switch box pin again or by performing the unhilite -all command. If it is necessary to make a bank shot through a switch box, select the local line resources used by the bank shot in the appropriate order and then perform the route command.

If you make a mistake while selecting resources for manual routing, you can deselect selected objects prior to performing the route command. If something routes that you want unrouted, select the signal name, signal pin, or route segment that you want to unroute and perform the unroute command. Unrouting a local line will free up that local line, which means that any switch box connection to that line will be unrouted also.