22Chapter 1 Graphics PassNot all GPL commands and data sent to the printer need to be in apass. In fact, many commands must be outside of a pass to functionproperly. For instance, the command ^H sets the form length if it isused outside of a pass, but sets the pass height if it is used within aPass.At this point, it may seem difficult to decide when to use a GraphicsPass. If there is any doubt about whether a command should goinside or outside of a pass, refer to Appdendix F, “Command Table”on page 287. The GPL commands fall into two general categories:Inside A Pass• GPL positioning commands (e.g., tabs, vertical justification, etc.)• GPL printing commands (e.g., barcodes, lines, boxes, certain fonts, etc.)• Block charactersOutside A PassGlobal Graphics Pass commands (i.e. commands which act on the entirepass as a unit, such as those which cause the entire Pass to be repeated orstored in memory for later use).Environmental commands wuch as form length setting, Graphics Mode, andFree Format.Non-GPL DataAny data you want to go to the current Control Panel emulation must be sentoutside of a Graphics Pass. Appdendix F, “Command Table” on page 287lists all GPL commands.Pass Spacing (Modplot)Code V output can be affected by a Plot Mode option that is available on yourprinter. Appendix G, “Modplot” on page 291 explains the Modplot option andhow it affects Code V output.Pass Buffer LengthData received from the host is stored in a Pass Buffer. The Printer begins toprocess a Graphics Pass when it receives a Pass Terminator. The printerprocesses one pass at a time, printing at the end of each pass. If the PassBuffer fills up before the printer encounters a Pass Terminator, it terminatesthe pass and attempts to process and print it.Buffered Form definitions and Repeat sequences cannot be processed untilthe Form or Repeat Terminator is received; therefore, the entire FormDefinition or Repeat Sequence must fit into the Pass Buffer to be printedcorrectly. Buffered Form execute data can be larger than the Pass Buffer. ThePrinter processes this data one Pass Buffer at a time, until the Form ExecuteTerminator is received.
