HP 300 Service Information Manual

Video BoardsGeneral DescriptionVideo boards allow the computer to send bit-mapped display information to medium or highresolution monitors. The user may upgrade his computer system from medium to high resolutionby installing a different board. Upgrading is accomplished through an exchange program. Itmay be performed by the user with common tools without CE support.One monochroillatic and two color video boards are available for the HP Series 300 computersystems. The color boards provide four-plane color display capability allowing the user to display16 colors from a palette of over 16 million colors. A description of these boards follows:• HP 98542A Mediulll-Resolution Monochromatic Video Board. This version displays 512X 400 pixels and drives the low resolution monochromatic monitors.• HP 98543A Medium-Resolution Color Video Board. This version displays 512 X 400 pixelpairs and drives the low-resolution color monitors.• HP 98544A High-Resolution Monochromatic Video Board. This version displays 1024 X768 individual pixels and drives the high-resolution color monitors.• HP 98545A High-Resolution Color Video Output Board. This version displays 1024 X768 individual pixels and drives the high-resolution color monitors.These boards make extensive use of large scale integrated (LSI) circuits. Up to four NMOSIII Display Controller chips provide an integrated bit mapped display with window-move hard-ware and frmne buffer support. Color mapping is entirely handled by another NMOS III chipcalled the Frame Buffer Controller. This chip performs color mapping and D to A conversion.Video memory consists of uses nibble-wide (4-bit) Display RAM (DRAM). The major differencebetween these assemblies is the amount of DRAM each has.Video boards perform the similiar functions, which are:• Establish display clock frequency in the computer system.• Initialize according to the specific monitor used.• Respond to interrupts on DIO bus to change color map data.• Control the display RAM maps.• Color boards output Red-Green/Sync-Blue Video to the color lnonitor.• Monochromatic boards output Video/Sync to the monochromatic monitor.Each of these is explained in the following functional description. Reference to Fig. 3-12 issuggested.60 Functional DescriptionArtisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com