1. xerox 560 computer system - The UK Mirror Service

Instruction NameMnemonicDesignationFunctionTranslate Byte StringTrans I ate and Test Byte Stri ngEdit Byte StringTBSTTBSEBSThese instructions are in the immediate byte operand classand are memory-to-memory operations. These operationsare under the control of information that must be loadedinto certain general registers before the instruction is executed.Except for the MOVE BYTE STRING instruction,which proceeds four bytes at a time under certain conditions,a byte string instruction proceeds one byte at a timeand may be interrupted after any individual byte operation.Upon return, execution resumes from the pointofinterruption.The general format for the information in the instructionword and in the general registers is as follows:Instruction word:Contents of register R:Contents of register Ru 1 :CountDesi gnationOperationRFunctionDesti nation nrlrlr~~~The 7-bit operation code of the instruction.(If any byte-string instruction isindirectly addressed, the basi c processortraps to location X l 40 1 at the time of operationcode decoding. )The 4-bit field that identifies register Rof the current general register block.Source Address(cont. )CountDestinationAddressbyte of the source byte string operand.The effective source address is the sourceaddress in register R plus the displacementvalue in the instruction word.An 8-bit field that contains the true count(from 0 to 255) of the number of bytesinvolved in the operation. This field isdecremented by 1 as each byte in thedestination byte string is processed. Ao count means IIno operation ll with respectto the registers and main memory.A 19-bit field that contains the byteaddress of the first (most significant)byte of the destination byte-string operand.This field is incremented by 1 aseach byte in the destination byte stringis processed.In any byte-string instruction, any portion of register Ror Ru1 that is not explicitly defined (i. e., bit positions8-12), should be coded with zeros for real and virtualaddressi ng.Since the value Ru1 is obtained by performing a logicalinclusive OR with the value 0001 and the value of theR field of the instruction word, the two control registersare Rand R + 1 if R is even. However, if R is an odd value,register R contains an address value that functions both as asource operand address and as a destination operand address.Also, if register 0 is designated in any byte-string instruc-... ___ 1 _______ .. ~ ___ TnA ... IC"1 ATe A"'I/""'\ TeC"T n'\rre C"TnT"'I"" ____ IIIVII \CAvCPI IVI "'\r\I'4"'LJ"'IL r\1'4V IL ... I U,I ........'\11'4'\,.7 UIIUEDIT BYTE STRING), its contents are ignored and a zerosource address value is obtained. Thus, the followingthree cases exist for most byte-string instructions, dependingon whether the value of the R field of the instruction wordis even and nonzero, odd, or zero:Case I, R is even and nonzeroThe effective source address is the address in register R plusthe displacement in the instruction word; the destinationaddress is the address in register R + 1, but without thedisplacement added.DisplacementMask/FillSource AddressA 20-bit field that contains a signedbyte displacement va lue, used to forman effective byte address. The displacementvalue is right-justified in the 20-bitfield, and negative values are in twolscomplement form.An 8-bit field used only with TRANSLATEAND TEST BYTE STRING and EDIT BYTESTRING. The purpose of this field isexplained in the detai led discussion ofthe TTBS and EBS instructions.A 19-bit field that normally contains thebyte address of the first (most significant)Case II, R is oddThe effective source address is the address in register R plusthe displacement in the instruction word; the destinationaddress is also the address in register R, but without thedisplacement added.Case III, R is zeroThe effective source address is the displacement value inthe instruction word; the destination address is the addressin register 1. In this case, the source byte-string operandis always a single byte.Byte-String Instructions 87