HP LaserJet 4250 Service Manual - Page 178
DIMM slots, Firmware DIMM (LJ 4200/4200L/4300 only), Nonvolatile memory, Memory Enhancement technology - print speed
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store a full page of print-image data before the data is sent to the print engine. Memory capacity can be increased by adding DIMMs to the formatter. Note that adding memory (DIMMs) might also increase the print speed for complex graphics. DIMM slots The DIMM slots can be used to add memory. In HP LaserJet 4200/4300 Series printers DIMM slots can also be used to add fonts or firmware upgrades. Firmware DIMM (LJ 4200/4200L/4300 only) To replace the printer firmware DIMM, insert a new firmware DIMM in DIMM slot 1 (the uppermost slot) inside the formatter assembly. See Firmware DIMM (LJ 4200/4300 only). CAUTION The firmware DIMM must be installed in slot 1 (formatter PCA location J1; topmost slot) Firmware can also be updated by downloading a remote firmware update (RFU). For more information about RFUs, see Downloading a remote firmware update. Nonvolatile memory The printer uses nonvolatile memory (NVRAM) to store I/O and information about the print environment's configuration. The contents of NVRAM are retained when the printer is turned off or disconnected. Memory Enhancement technology The HP Memory Enhancement technology (MEt) effectively doubles the standard memory through a variety of font- and data-compression methods. NOTE The Me t is only available in PCL mode; it is not functional when printing in PS mode. PJL overview Printer job language (PJL) is an integral part of configuration, in addition to the standard printer command language (PCL). With standard cabling, use PJL to perform a variety of functions, such as the following: ■ Two-way communication with the host computer through a bidirectional parallel connection. The printer can send the host computer information about such things as the control panel settings, and the control panel settings can be changed from the host through two-way communication. ■ Dynamic I/O switching. The printer can be configured with a host on each I/O by using dynamic I/ O switching. Even when the printer is offline it can receive data from more than one I/O simultaneously, until the I/O buffer is full. ■ Context-sensitive switching. The printer can automatically recognize the personality (PS or PCL) of each job and configure itself in that personality. ■ Isolation of print environment settings from one print job to the next. For example, if a print job is sent to the printer in landscape mode, the subsequent print jobs are prinedt in landscape mode only if they are formatted for it. 164 5 Theory of operation