HLASM: V1R6 Language Ref

USING instructionendrange of an active USING instruction. The range of an active USING isconsidered to be that which is valid for generating 12-bit or 20-bitdisplacements.specifies the end address, which can be a relocatable or an absolute expression.The value of the expression must lie between 0 and 2 31 −1. The end addressmay exceed the (base address + default range) without error. The end addressmust be greater than the base and must have the same relocatability attributes.The implicit address denoted by address specifies the address where base is to bebased, and is known as the supporting base address. As address is a relocatableexpression, it distinguishes a dependent USING from an ordinary USING. Theassembler converts the implicit address denoted by address into its explicitbase-displacement form. It then assigns the base register from this explicit addressas the base register for base. The assembler assumes that the base register containsthe base address base minus the displacement determined in the explicit address.The assembler also assumes that address is appropriately aligned for the code basedon base. Warnings are not issued for potential alignment problems in thedependent USING address.A dependent USING depends on the presence of one or more correspondinglabeled or ordinary USINGs being in effect to resolve the symbolic expressions inthe range of the dependent USING.The following example shows the use of an unlabeled dependent USING:EXAMPLE CSECTUSING EXAMPLE,R10,R11 Ordinary USING..USING IHADCB,DCBUT2 Unlabeled dependent USINGLH R0,DCBBLKSI Uses R10 or R11 for BASE..DCBUT2 DCB DDNAME=SYSUT2,...The following example shows the use of two labeled dependent USINGs:EXAMPLE CSECTUSING EXAMPLE,R10,R11 Ordinary USING..DCB1 USING IHADCB,DCBUT1 Labeled dependent USINGDCB2 USING IHADCB,DCBUT2 Labeled dependent USINGMVC DCB2.DCBBLKSI,DCB1.DCBBLKSI Uses R10 or R11 for BASE..DCBUT1 DCB DDNAME=SYSUT1,...DCBUT2 DCB DDNAME=SYSUT2,...Range of a dependent USING instructionThe range of a dependent USING instruction (called the dependent USING range)is either the range as specified by the range end, or the range of the correspondingUSING minus the offset of address within that range, whichever is the lesser. If thecorresponding labeled or ordinary USING assigns more than one base register, themaximum dependent USING range is the composite USING range of the labeledor ordinary USING.Chapter 5. Assembler instruction statements 225