Xerox 4400DT Service Manual - Page 435

Engine Logic Board and Front Panel Functions The Engine Logic Board performs eight main functions: I Communicates with the Image Processor. I Controls the print sequence. I Controls the Fuser Assembly, Laser Assembly, and Drive components. I Distributes low DC voltages to various printer components. I Monitors printer status. I Maintains a running print count. I Writes the NVRAM settings. I Controls printer options. The Engine Logic Board uses a 32 bit microcomputer and Application Specific Integrated Circuits (ASICs). The 32 bit microcomputer includes: ROM, RAM, a 16 bit integrated timer, a programmable timing pattern controller, a watch dog timer, serial communication interfaces, an A/D converter, a D/A converter, I/O ports, a DMA controller, and a refresh controller. Image Processor Board The Image Processor (IP) is one of the major elements that make up the Phaser 4400 printer. The primary function of the Image Process is to receive Host data through one of the following available ports (Parallel, USB, or Ethernet). The received host data is buffered and stored and sent to the print engine in a rasterized format. The secondary function of the Image Processor is to provide print control, front panel control, configuration setup, error reporting and job recovery. Before the IP can receive and process data it must first pass the Power On Self Test (POST). This test process verifies proper operation of the Image Processor and prepares it for processing the host data by putting the Image Processor in a known state. The Image Processor connects to the Engine Logic Board directly. The Front Panel is connected to the Image Processor and signals pass through the Engine Logic Board via the Image Processor. 5 VDC PWB This board converts 24 VDC from the LVPS to 5 VDC, which it supplies to the Image Processor board. 8-22 Phaser 4400 Laser Printer Service Manual