HP 750c Service Manual - Page 46

ASICs On the main PCA, the processorĆsupport ASIC is designed to manipulate swath data into the actual firing order for the nozzles on the four cartridges that are mounted on the carriage assembly. The processorĆsupport ASIC receives pixels from the physical swath RAM and sends them serially to the carriage ASIC. A main processor on the main PCA controls all plotter operations with the help of the processorĆsupport ASIC and the servo processor. Communications between the servo processor and the main processor take place through registers in the processorĆsupport ASIC. The processorĆsupport ASIC provides pulseĆwidthĆmodulated signals to the YĆaxis (carriageĆaxis) and the XĆaxis (mediaĆaxis) motor drivers, to drive the YĆaxis and the XĆaxis motors. The linear encoder connected to the carriage PCA gives the processorĆsupport ASIC feedback about the position of the carriage. The XĆaxis motor encoder on the XĆaxis motor gives the processorĆsupport ASIC feedback about the position of the XĆaxis motor. In addition, the processorĆsupport ASIC contains a DRAM controller that generates multiplexor controlĆandĆenable strobes for the DRAM row and column addresses during a memory access. The DRAM controller also arbitrates between a memory request and a refresh request and performs the refresh operation. Servo Processor The servo processor communicates with the main processor through registers in the processorĆsupport ASIC. The servo processor writes information into the registers and sends an interrupt to the main processor. The main processor then reads the registers, and the interrupt is automatically cleared. Using this procedure, the servo processor provides the main processor with information from the plotter sensors. The sensors give the main processor the ability to check status conditions. The servo processor controls the: D Servo motors. D Front panel. D Fan. D Sensors. D Electrically erasable readĆonly memory (EEROM). D Stepper motors. Stepper Motors There are three types of stepper motors: D The primer stepper motor is used to drive the nozzle primer. D The bail stepper motor drives the bail. D The wiper stepper motor drives the orthogonal wiper. 5-4 Functional Overview C4705-90000