User Guide

5.7 Forward&BackAnnotation

A schematic file and the associated board file are logically linked by

automatic Forward&Back Annotation. This ensures that the schematic

andtheboardarealwaysconsistent

As soon as a layout is created with the BOARD command (or by means

of the Switch to board icon), the two files are consistent. Every action

performed on the schematic diagram is simultaneously executed in the

layout. If, for instance, you place a new device, the associated housing

will appear on the layout at the edge of the board. If a net is placed, the

signal lines are simultaneously drawn in the layout. Certain operations

such as the placement or deletion of signals are only allowed in the sche

matic. The Layout Editor does not permit these actions, and issues an

appropriate warning. Renaming devices or changing their values, for ex

ample,arepermittedinbothfiles.

The EAGLE help pages contain a closer description of the technical

details.

It is not necessary for you, as the user, to pay any further attention to

this mechanism. You only have to ensure that you do not work on a

schematic whose associated board file has been closed, and vice versa.

This means that both files must always be loaded at the same time. Oth

erwisetheylooseconsistency,andtheannotationcannolongerwork.

If you have, however, once edited the board or the schematic separately,

the electrical rule check (ERC) will check the files for consistency when

they are loaded. If inconsistencies are found, the ERC opens an error

file with appropriate messages about the schematic diagram and the

layout.

Correct the layout or the schematic diagram in accordance with the er

ror messages in the ERC file. Run the ERC frequently to check prog

ress, until the two files are consistent again. The message at the end of

theERCfilemustbe:

Boardandschematicareconsistent.

Thensavethefiles.

EAGLEManual