HP 1200 Service Manual - Page 75

Basic sequence of operation (formatter-toprinter) The operation sequence of the printer is controlled by the microprocessor (CPU) on the ECU. The following events take place during normal printer operation: Table 12. Basic sequence of operation Period Purpose Remarks WAIT After the printer is turned on until the end of the initial rotation of the main motor. To clear the drum surface of potential and to clean the primary charging roller. Detects whether or not the cartridge is installed. STBY (Standby) From the end of the WAIT period or the LSTR period until the pickup command is input from the formatter. Or, from the end of the LSTR period until the printer is turned off. To keep the printer ready to print. INTR (Initial Rotation Period) After the pickup command has been input from the formatter until the media reaches the paper top sensor (PS402). To stabilize the photosensitive drum sensitivity in preparation for printing. Also to clean the primary charging roller. PRINT (Print) From the end of the initial rotation until the primary voltage goes OFF. To form images on the photosensitive drum based on the VIDEO signals (/VDO, VDO) input from the formatter and to transfer the toner image onto the media. LSTR (Last Rotation Period) After the primary voltage goes OFF until the main motor stops rotating. To deliver the last page. Also to clean the primary charging roller. When the pickup command is input from the video controller, the printer enters the INTR period immediately after the end of the LSTR period. EN Optional copier/scanner 73