Xerox 1235/DX Service Guide - Page 17

Printer RAM and printer capabilities The printer features three DIMM connectors which accept 64-, 128-, and 256-Mbytes RAM DIMMs. The printer can use off-the-shelf RAM meeting these specifications: s 168-pin DIMM s Synchronous DRAM s 3.3 volt s 9 nsec speed s Valid on-board Serial Presence Detect ROM. The Startup page and the Configuration Page list the amount of RAM installed in the printer. Upon power-up, the image processor interrogates the 256 byte Serial Presence Detect ROM which describes the DIMM with details such as data width, clock delay, number of address columns and row, refresh rate and more. If the DIMM does not meets the required specifications it the printer reports and "Invalid Memory DIMM Configuration" message and stops the booting process. If the power-up self-test diagnostics detect a DIMM with defective memory cells the printer declares "Diagnostics Failed - Press Enter to Continue." After the enter key is pressed the boot process continues and the defective RAM DIMM is ignored. Note that a seriously defective RAM DIMMs (with grounded address lines, for example) can keep the system controller board from booting up at all. With more memory the printer gains the capabilities of printing without having to use image compression (which trades less installed RAM for longer image processing time) and dual frame buffers for printing one image while processing a second image (which gives greater printing throughput). The printer features three slots each of which can contain a 64-, 128-, or 256-Mbytes SDRAM DIMM. Any slot may be used for any size DIMM. However, 256 Mbyte RAM DIMMs cannot be mixed with smaller RAM DIMMs. DRAM memory totalling beyond 512 Mbytes will be ignored. The image-processing controller board also contains 16 Kbytes of non-volatile memory (NVRAM), to store all for the necessary values that can be set on the printer. CRU life counter behavior Internal counters track customer replaceable unit (CRU) life usage and store the values in NVRAM. The controller monitors these counters in order to display the near end of use and end of use messages. The toner states displayed are OK, Low, and Empty, where the engine senses and automatically reports the Low and Empty states. When the empty state is reached for toner, the printer terminates printing at the end of current page and displays the appropriate message on the control panel. No further jobs are accepted from any input port. 4 Phaser 1235 Network Color Printer