W820 (4025-xxx)

4025-XXX3. Output to motors, solenoids, and other componentsAfter comparing input values with timing and reference values, the MCU makes adecision on the current status of the printer and responds appropriately. The MCUmay switch on or off motors, solenoids, or other components. The MCU may alsosignal that an error occurred.Example follows:At the start of a print cycle, the MCU switches on the Main Drive Motor, and then theFeed Clutch. The MCU uses the Feed Clutch actuation as a timing marker. The FeedRolls attached to the Feed Clutch drive a sheet of paper out of the paper tray anddown the paper path. As the sheet of paper travels down the paper path it strikes theRegistration Sensor. The Sensor sends a signal to the MCU PWB telling it that thepaper has arrived. The MCU takes the elapsed time from when it actuated the FeedClutch to the time it received the signal from the Registration Sensor and comparesthat time with the set time (or expected time) that is stored in ROM on the MCUPWB. If the time elapsed is within range, the print cycle continues. If the timeelapsed is slower than the set time or if there was no signal from the RegistrationSensor within the set time, the MCU interprets that as an error and sends a 200Registration Jam status to the ESS PWB.4. Processing image dataAlthough the MCU PWB does control and monitor the operation of the Printhead, theactual video data sent by a host computer bypasses the MCU PWB on its way to theLaser Diode PWB.Example follows:Video data originating from either a local computer or a network computer entersthe printer through the ports in the ESS PWB. The ESS PWB stores and buffers theraw data and then converts it to rasterized data that controls the Laser Diode. Therasterized data leaves the ESS PWB and enters the MCU PWB. The MCU PWBdoes not buffer nor process the data, it simply passes it along as a video signal tothe Laser Diode PWB. The video signal switches the Laser Diode on and offaccording to the image information sent in the raw data.1-26 Service Manual