41154001TH Rev.2 18 /2.1 Main Control BoardThe main control board consists of a single chip CPU, two program/font ROMs, two DRAMs, anEEPROM, a host interface circuit, and a mechanism driving circuit.(1) Single chip CPUThe single chip CPU is a custom CPU (32-bit internal bus, 32-bit external bus, 28.24-MHzclock, with input frequency from a 7.06-MHz clock) which incorporates the RISC CPU and itsperipheral devices, and has the following functions:(2) Program and Font ROMsThe Program and Font ROMs store the equipment program and various types of fonts. MaskROM is used as Program and Font ROMs. The mounting locations of these Program and FontROMs vary depending on the type of the ROMs.(3) DRAMThe DRAM is a 4MB resident memory on the main control board that stores edited data, imagedata, DLL data and macro data.(4) EEPROM4Kbit Electrically Erasable PROM (EEPROM), is loaded with the following kinds of data:• Menu data• Various counter data (page counter, drum counter)• Adjusting parameters (LED head drive time, print start position, paper feed length)(5) Parallel InterfaceParallel data is received from a host system via parallel interface which conforms to theIEEE1284 specification.Built-in device FunctionChip select controllerBus controllerDRAM controllerDMA controllerParallel interface controllerSerial interface controllerVideo output portLED STB output portTimerSerial I/O portI/O portControl of ROM, DRAM and I/O deviceTransfer of image data from DRAM to video output portControl of Centronics parallel interfaceControl of RS-232C serial interfaceControl of LED headGeneration of various control timingMonitoring of paper running and paper sizeControl of operator panel, EEPROM, and optionsInput and output of sensor and motor signals
