Used in photoplotting. D-Code consists of X,Y coordinates supplemented by commands that define where the PCB image starts, what shape it will take, and where it ends. In addition to the coordinates, Gerber data contains aperture information, which defines the shapes and sizes of lines, holes, and other features. These Gerber files are generated using the aperture sizes available in the Aperture Table.
These apertures are defined in terms of a format recognized by the photoplotter. All the available D-codes and the sizes they represent are listed in Aperture Table. The interpretation and repertoire of D-codes may vary depending on the make and model of the photoplotter. For example D-code D100* may result in one machine as a .062″ line and on another as a .100″ line. There are photoplotters which allow flexible D-code-to-aperture assignment. For certain others the repertoire of D-codes may be fixed. Latest photoplotters available in the market may recognize various D-codes for creating different shapes. There are three DCodes for each available aperture size, namely for plotting lines, flashing round pads and flashing square pads which are recognized by almost all standard photoplotters.
When using extended Gerber format, the user does not have to bother about these Aperture Tables as the system automatically generates the required aperture parameters in the Gerber file.
D codes have multiple purposes. D-codes control the aperture size or rather the Aperture’s position on the list or wheel. D code with values of 10 or greater represent aperture size of the photoplotter the Aperture’s position on the list or wheel. D codes also control the state of the light being On or Off. There are three standard D-Codes provided for this purpose:
- D02* instructs the photoplotter to move to the given X-Y position with Light Off (Move Command).
- D01* instructs the photoplotter to move to the given X-Y position with Light On. (Draw Command) thus plotting traces.
- D03* instructs the photoplotter to create a flash at the given X-Y position i.e. Light On, Light Off at the given position thus plotting pads.
D10 and higher value refer to corresponding aperture shapes and dimensions assigned to them by each individual user based on the photoplotter he intends to use.