Compuprint 4247-Z03 Programmer Manual - Manual (Page 176)

Self-Describing Instructions
This portion of the Graphic Data Descriptor structured field contains zero or more self-describing
instructions that set the drawing defaults for the graphics picture. The general format of a self-describing
instruction is:
21 Length Set Mask Default Data
The first byte, 21, indicates that the following parameter is a Set Current Defaults instruction.
The Length byte is the length of the following data. If this value equals 4, the printer uses the standard
default values.
The Set byte indicates the type of attribute or parameter this instruction is specifying.
The bits 0 through 15 in the Mask bytes correspond to attribute items within the indicated set. The
individual set descriptions explain the meanings of these bits. When a mask bit equals one, the value of
the default byte selects one of two options. See the default byte description for details. When a mask bit
equals zero, the default does not change and the data does not include the value for the corresponding
attribute.
The Default byte has a value of either 0F or 8F. A value of 0F sets all indicated items to their standard
default values. A value of 8F and a mask bit equal to one requires the appropriate data for a new default
to be defined in the data field for the corresponding attribute. Unreferenced data bytes not addressed by
the mask field are ignored.
Figure 25. Position-and-Trim Mapping
156 Programmer Manual