Geode GXLV Processor Series Low Power Integrated x86 Solutions

Geode GXLV Processor SeriesIntegrated Functions (Continued)4.4.2 Master/Slave RegistersWhen starting a BitBLT or vector operation, the graphicspipeline registers are latched from the master registers tothe slave registers. A second BitBLT or vector operationcan then be loaded into the master registers while the firstoperation is rendered. If a second BLT is pending in themaster registers, any write operations to the graphicspipeline registers will corrupt the values of the pendingBLT. Software must prevent this from happening by checkingthe “BLT Pending” bit in the GP_BLT_STATUS register(GX_BASE+820Ch[2]).Most of the graphics pipeline registers are latched directlyfrom the master registers to the slave registers whenstarting a new BitBLT or vector operation. Some registers,however, use the updated slave values if the master registershave not been written, which allows software to rendersuccessive primitives without loading some of theregisters as outlined in Table 4-20.4.4.3 Pattern GenerationThe graphics pipeline contains hardware support for 8x8monochrome patterns (expanded to two colors), 8x8dither patterns (expanded to four colors), and 8x1 colorpatterns. The pattern hardware, however, does not maintaina pattern origin, so the pattern data must be justifiedbefore it is loaded into the GXLV processor’s registers. Forsolid primitives, the pattern hardware is disabled and thepattern color is always sourced from theGP_PAT_COLOR_0 register (GX_BASE+8110h).Table 4-20. Graphics Pipeline RegistersMasterGP_DST_XCOORGP_DST_YCOORGP_INIT_ERRORGP_SRC_YCOORFunctionNext X position along vector.Master register if written, otherwise:Unchanged slave if BLT, source mode = bitmap.Slave + width if BLT, source mode = text glyphNext Y position along vector.Master register if written, otherwise:Slave +/- height if BLT, source mode = bitmap.Unchanged slave if BLT, source mode = text glyph.Master register if written, otherwise:Initial error for the next pixel along the vector.Master register if written, otherwise:Slave +/- height if BLT, source mode = bitmap.www.national.com 126 Revision 1.3