Program Logic Manual - All about the IBM 1130 Computing System

Dummy one - word entry in CALL TV(if necessary) to ensure odd addressfor FACLast Second First Indicators FAC Last Second FirstLIBF LIBF LIBF CA LL CALL CALL151 I- I I I I I I I Jf.48— LowCore tt_HighCoreL_Figure 10. Layout of the Transfer VectorLIBF TV CALL TV COMMONTransfer Vectorfetching it first, if necessary. It does likewise fora SOCAL, except that it is never entered if a subprogramis called that is a part of the SOCAL currentlyin the SOCAL area (see Linkage to the SystemOverlays).The Flipper Table immediately precedes theflipper. It consists of a 6-word entry for each entrypoint specified in the LOCAL information in the SCRA(for a given mainline) that is referenced by a CALLand a 5-word entry for each entry point referenced bya LIBF'. If a subprogram has more than one entrypoint but only one is specified in the LOCAL information(a specified LOCAL), there is a Flipper Tableentry for each entry point referenced in the coreload.The format of a 5-word (LIBF) entry in theFlipper Table is as follows:WordDescription1-2 BSI L FL0003 Word count of the subprogram4 Sector address of the subprogram5 Entry point address in the subprogramThe format of a 6-word (CALL) entry in theFlipper Table is as follows:WordDescription1 Link word2-3 BSI L FLO104 Word count of the subprogram5 Sector address of the subprogram6 Entry point address in the subprogramLinkage to the System Overlays (SOCALs)In order to assure very fast transfer to a subprogramthat is a part of a SOCAL that is in core storage ata given time, special transfer vector entries aremade for SOCAL subprograms. They are differentfrom the standard LIBF and CALL linkages, and theyare different from the linkage to a LOCAL. TheSOCAL transfer time is approximately 20 microseconds,compared to 150-180 microseconds 'to aLOCAL. (Both timings assume a 3.6 microsecondstorage cycle.)Figure 11 shows an entry in the LIBF TV for anin-core subprogram (entry 2) and the special Linkagein the LIBF TV for SOCAL subprograms (entries3-8). Entry 1 is the LIBF TV entry for a SOCALsubprogram. The "disp" is a displacement to thesecond word of the linkage for the SOCAL in whichthe subprogram is found.The example represented in Figure 11 is one thatrequires SOCAL option 2; TV entries 5 and 8 wouldnot appear if option 1 were used. Entry 1 is thelast entry in the LIBF TV, i. e. , the highestaddressedword of the transfer vector. Suppose that(1) a LIBF to FADD were made and (2) SOCAL 1 werenot in core. The LIBF would be a BSI to the firstword of entry 1, which would then BSI to the secondword of entry 3. Entry 3 would MDX to the firstword of entry 6, which would transfer control to theLOCAL/SOCAL flipper subroutine (FLIPR) atFL230, the entry point in FLIPR for fetching thearithmetic subprograms. The flipper would fetchSOCAL 1, change the third word of entry 3 to MDXto *-3, and BSC to the first word of entry 3, whichthen transfers control to FADD. The flipper wouldalso ensure that the third words of entries 4 and 5were both MDX to *-12.38