1. xerox 560 computer system - The UK Mirror Service

Normally, bit positions 15-31 may be ignored insofar as theoperation of the MMC instruction is concerned. The resultsof the instruction are the same whether MMC is indirectlyor directly addressed. However,if MMC is indirectly addressedand the indirect reference address is nonexistent,the nona II owed operation trap (location X' 40 ' ) is activated.The R field, which must be coded with an even value, designatesan even-odd pair of general registers (R and Ru1)that contain additional control information required by theMMC instruction. If the R fi eld is coded with an odd va I uea trap to location X'4D ' (instruction exception trap) occurs.Depending upon the type of addressing, the contents ofregister R may be as follows:If MA = 0, contents of register Rare:The Control Start field (bit positions 15-20, 21, or 22)points to the beginning of the memory region controlled bythe registers to be loaded. The significance of this fieldis different for the 5 modes of MMC operations and is describedwithin each mode below.Affected: (R),(Ru1),memory controlstorageCONTROL IMAGELOADING THE MEMORY MAPT raps: Instruction exception,nonallowed operation.Each word of the memory map control image contains eitherfour a-bit page addresses or two ll-bit extended page addresses,as illustrated below:Typical memory map control image word (a-bit format):If MA = 1 and MM = 0, the contents of register Rare:Typical memory map control image word (ll-bit format):In either case, the Control Image Address is the virtual addressof a control word within the control image area to beloaded into a block of memory control registers, as specifiedby the contents of register Ru 1.Depending upon the type of control image being loaded,the contents of register Ru 1 may be in one of the followingthree formats:Depending upon the memory map control image format, theinstruction format is one of the following:LMAPLOAD MAP (a-bit format)For loading memory map image (either a-bit or 11-bit format),contents of register Ru 1 are:LMAPRELOAD MAP REAL EXTENDED (ll-bit format)For loading 4-bit write lock images, contents of registerRu1 are:Depending upon the type of addressing, the format of registerR contents is one of the following:If MA = 0;For loading access protection or 2-bit write lock images,contents of register Ru 1 are:Map lma~e AddressIIf MA = 1 and MM = 0;The Count field (bit positions 0-7) specifies the numberofwords to be loaded from the control image area. If theinitial word count is zero, a word count of 256 is implied.114 Controi Instructions