Compuprint 4247-Z03 Programmer Manual - Manual (Page 106)

v The pels of a rule
v The one pels of an image
v The pels of a graphic line or arc
v The one pels of a filled area
v The one pels of a bar code.
Background pels are all other pels.
Text data, because it prints at a different physical resolution than the data in the other blocks, does not
logically mix with any other data type. The only mixing that takes place between text data and any other
data type is the (possible) physical mixing of ink on forms.
For the 4247 Printer, the mixing rule for overwritten data within a given block of image, graphics, or bar
code data is quite simple: background pels are transparent; foreground pels are opaque. Thus,
background pels always show through what is underneath (what was received earlier), while foreground
pels cover it up. In other words, a pel prints in the color of its last overwriting.
Note: Color of medium is a valid color for image, graphics, and bar code data. Thus, foreground pels in
this color cover up pels of any other color that are underneath.
For the 4247 Printer, the mixing rule for overwritten data across blocks is the same as it is within blocks
except for text. Thus, across image and graphics, or bar code blocks, background pels are transparent,
while foreground pels are opaque.
IPDS Operating States
There are various operating states using the IPDS commands. The following states define the operating
environment for this printer:
v
Home state
v Page state
v Overlay state
v Page segment state
v Block state.
While in the page, overlay, or page segment state, the printer can enter a block state. The block state
causes the printer to process a block of data. There are image blocks, graphics blocks, and bar code
blocks. Thus, the printer can enter any of the data block states from any of the operating states.
Home State
Home state is the initial IPDS operating state. The printer returns to home state at the end of each page,
page segment, or overlay. In addition, the printer can enter the home state by receiving a Set Home State
command. The 4247 Printer also goes to home state when a NACK is returned.
While in the home state, the printer receives control and initialization commands to prepare for a print
operation. In this state, the printer can also receive commands that request the return of printer information
to the host application program.
Page State
Page state is the operating state for printing a logical page. The printer enters the page state from the
home state as a result of receiving a Begin Page command.
In the page state, the printer can receive commands that merge previously defined and loaded overlay and
page segments with the current page information. The printer can also receive Write Text commands that
position text on the logical page. The presence of Write Image (block) Control, Write Graphics (block)
86 Programmer Manual