Programming Interface Information:
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SEGG
PrologControl Block Contents
SEGG DSECT
Storage Layout
Cross Reference
SEGG Prolog
NAME : HCPSEGG DESCRIPTION: ESAME Segment Table Entry DSECT : SEGG Function : There is one ESAME segment table entry for each megabyte of address space. A segment table is made up of contiguous segment table entries. The format of the segment table entry is ARCHITECTED and cannot be changed in any way which violates the architecture. Notes : the ESAME segment table entry does not contain a page table length. In ESAME mode, all page tables represent a full megabyte of virtual storage (256 page table entries).
SEGG Control Block Content
SEGG DSECT
Hex Dec Type/Val Lng Label (dup) Comments ---- ---- --------- ---- -------------- -------- 0000 0 Structure SEGG ESAME Segment Table Entry 0000 0 Dbl-Word 8 SEGGENTR ESAME format segment table entry 00000008 SEGGLEN *-SEGGENTR Length of one ESAME format segment table entry 0008 8 Dbl-Word 8 SEGGNEXT (0) Next ESAME segment table entry 0000 0 Signed 4 SEG64W0 Word 0 of ESAME STE. Bits 0-31 of ESAME PTO. 0004 4 Signed 4 SEG64W1 Word 1 of ESAME STE 0004 4 Bitstring 1 * (2) Bits 32-47 of ESAME PTO 0006 6 Bitstring 1 * Bits 48-52 of ESAME PTO, plus the following three bits .... ..1. SEGGPROT X'02' Entire segment is page protected 0007 7 Bitstring 1 SEGGSTAT Segment Table Entry Status ..1. .... SEGGINVL X'20' Segment Table Entry is invalid. Bits 0-52 of the Segment Table entry do not contain a valid Page-Table Origin. ...1 .... SEGGCOMN X'10' Common segment bit .... 11.. SEGGTTBT X'0C' Table Type bits - must be B'00' SEGGSTAT SEGGPTMH X'FFFFFFFF' Isolate page-table origin - High SEGGSTAT SEGGPTML X'FFFFF800' Isolate page-table origin - Low SEGGSTAT SEGG2GMH X'FFFFFFFF' Isolate STE bits which must be zero in a <2G ESAME STE - High .... .... SEGG2GML X'80000000' Isolate STE bits which must be zero in a <2G ESAME STE - Low SEGGSTAT SEGGPROM X'00000200' Isolate segment page protect bit ..1. .... SEGGINVM X'00000020' Isolate invalid bit ...1 .... SEGGCOMM X'00000010' Isolate common-segment bit ...1 .1.. SEGGSHFT 20 Bits to shift by to convert between segment number and virtual address. SEGGSTAT SEGGPTUN 2048 Number of bytes in a page-table. In ESAME, all page tables are "full" page tables containing 256 8 byte entries, representing 1M of virtual storage. .... 1.11 SEGGPTUS 11 Number of bits to shift left in order to multiply by SEGPTUNT. .... 1... SEGGPXNUM 8 Number of bits in a PX 1111 1111 SEGGPXRIT X'FF' Mask to isolate a right- justified PX ...1 .1.. SEGGPXPT 12+8 Bits to shift right an isolated page index to obtain a page- table length. .... 1..1 SEGGPXDS 12-3 Bits to shift to convert between an isolated page index and the displacement into the page table of applicable 8 byte ESAME PTE.
SEGG Storage Layout
*** SEGG - ESAME Segment Table Entry * * +-------------------------------------------------------+ * 0 | SEGGENTR | * +-------------------------------------------------------+ * *** SEGG - ESAME Segment Table Entry *** Overlay for SEGGENTR in SEGG * * +---------------------------+---------------------------+ * 0 | SEG64W0 | SEG64W1 | * +---------------------------+---------------------------+ * 8 * *** Overlay for SEGGENTR in SEGG *** Overlay for SEG64W1 in SEGG * * +-------------+------+------+ * 0 ... 4 |/////////////|//////|:GSTAT| * +-------------+------+------+ * 8 * *** Overlay for SEG64W1 in SEGG
SEGG Cross Reference
Symbol Dspl Value -------------- ---- ----- SEGGCOMM 0007 10 SEGGCOMN 0007 10 SEGGENTR 0000 SEGGINVL 0007 20 SEGGINVM 0007 20 SEGGLEN 0000 00000008 SEGGNEXT 0008 SEGGPROM 0007 SEGGSTAT SEGGPROT 0006 02 SEGGPTMH 0007 SEGGSTAT SEGGPTML 0007 SEGGSTAT SEGGPTUN 0007 SEGGSTAT SEGGPTUS 0007 0B SEGGPXDS 0007 09 SEGGPXNUM 0007 08 SEGGPXPT 0007 14 SEGGPXRIT 0007 FF SEGGSHFT 0007 14 SEGGSTAT 0007 SEGGTTBT 0007 0C SEGG2GMH 0007 SEGGSTAT SEGG2GML 0007 00 SEG64W0 0000 SEG64W1 0004
Last updated on 29 Mar 2001 at 15:10:26 EDT.
Copyright IBM Corporation, 1990, 2001