In a message dated 12/18/2006 10:57:43 P.M. Central Standard Time, rfochtman [at symbol] YNC.NET writes:
>You said it yourself: no references for OPERANDS. But if INSTRUCTION FETCH has to cross a boundary to an invalid page, an exception can still occur. There are many instructions like LA for which the Principles of Operations says "Program Exceptions: None." Others are Branch on Count/Index High/Index Low or Equal and a gazillion others, give or take a passel. Within the description of each instruction is a section beginning with "Program Exceptions: xxxx". What kinds of program exceptions are included in xxxx? Look at the beginning of the text for General Instructions (chapter 7) in the PoOps and there is the following: "the exceptional conditions in operand designations, data, or results that cause a program interruption." Load Address has no possible exceptional conditions of these types, all three of which imply that execution of the instruction was attempted. But before execution can be attempted, the instruction must be fetched. Every instruction is capable of producing a program exception, such as a S0C4, if some part of the instruction cannot be fetched, including even 2-byte-long instructions like SR where no page boundary crossing exists. Some times you cannot even access the first byte of the instruction. Bill Fairchild ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
