Programming Interface Information: This information is NOT intended to be used as Programming Interfaces of z/VM.

#### SEG39

Prolog

Control Block Contents
SEG39 DSECT

Storage Layout

Cross Reference (Contains links to field and bit definitions)

#### SEG39 Prolog

     NAME       : HCPSEG39
     DESCRIPTION: ESA/390 - Segment Table Entry
     DSECT      : SEG39
     Function   : There is one segment table entry for each ESA/390
                  megabyte of address space.  A segment table is
                  made up of contiguous segment table entries.
                  The format of the ESA/390 segment table entry is
                  ARCHITECTED and cannot be changed in any way
                  which violates the architecture.

#### SEG39 Control Block Content

#### SEG39 DSECT

    Hex   Dec Type/Val   Lng Label (dup)    Comments
    ---- ---- --------- ---- -------------- --------
    0000    0 Structure      SEG39          ESA/390 - Segment Table Entry
    0000    0 Signed       4 SEGENTRY       Pointer to page table on 64 byte
                                            boundary.
              00000004       SEGLENTH       *-SEGENTRY Length of 1 segment
                                            table entry
    0004    4 Signed       4 SEGNEXT (0)    Next segment table entry
    0000    0 Bitstring    1 *              Bits 0-7 of page table origin.
                                            Bit 0 must be 0 in a valid STE.
    0001    1 Bitstring    1 *              Bits 8-15 of page table origin
    0002    2 Bitstring    1 *              Bits 16-23 of page table origin
    0003    3 Bitstring    1 SEGSTAT        Segment table entry status. Left
                                            2 bits are bits 24-25 of PTO. (6
                                            bits appended on right form the
                                            page table origin.)
              ..1. ....      SEGINVAL       X'20' SEGINVAL Segment table
                                            entry is invalid
              ...1 ....      SEGCOMMN       X'10' SEGCOMMN Common segment bit
              .... 1111      SEGPTLNG       X'0F' SEGPTLNG Page table length
                                            (in units of 64 byte blocks,
                                            minus 1).
              0SEGSTAT       SEGPTOM        X'7FFFFFC0' SEGPTOM Isolate
                                            page-table origin
              ..1. ....      SEGINVM        X'00000020' SEGINVM Isolate
                                            invalid bit
              ...1 ....      SEGCOMM        X'00000010' SEGCOMM Isolate
                                            common-segment bit
              .... 1111      SEGPTLM        X'0000000F' SEGPTLM Isolate
                                            page-table length Notes : Since
                                            ESA/390 segment tables may be
                                            longer (up to 8K) than their
                                            boundary alignment (4K), a STO
                                            can not be computed from an STE
                                            address via a mask.
              ...1 .1..      SEGSHIFT       20 SEGSHIFT Bits to shift right
                                            to get segment number from an
                                            address or shift left to get
                                            starting segment address from a
                                            segment number
              .1.. ....      SEGPTUNT       64 SEGPTUNT Number of bytes in a
                                            "page-table unit", the number of
                                            bytes in the smallest variation
                                            of the size of a page table.
              .... .11.      SEGPTUNS       6 SEGPTUNS Number of bits to
                                            shift left in order to multiply
                                            by SEGPTUNT.
              ...1 ....      SEGPXPTL       12+4 SEGPXPTL Bits to shift right
                                            an isolated page index to obtain
                                            a page- table length.
              .... 1.1.      SEGPXDSP       12-2 SEGPXDSP Bits to shift right
                                            an isolated page index to obtain
                                            the displacement into the page
                                            table of the applicable PTE.

#### SEG39 Storage Layout

    *** SEG39 - ESA/390 - Segment Table Entry
    *
    *     +---------------------------+
    *   0 |         SEGENTRY          |
    *     +---------------------------+
    *
    *** SEG39 - ESA/390 - Segment Table Entry

    *** Overlay for SEGENTRY in SEG39
    *
    *     +------+------+------+------+
    *   0 |//////|//////|//////|:STAT | 4
    *     +------+------+------+------+
    *
    *** Overlay for SEGENTRY in SEG39

#### SEG39 Cross Reference

    Symbol         Dspl Value
    -------------- ---- -----
    SEGCOMM        0003 10
    SEGCOMMN       0003 10
    SEGENTRY       0000
    SEGINVAL       0003 20
    SEGINVM        0003 20
    SEGLENTH       0000 00000004
    SEGNEXT        0004
    SEGPTLM        0003 0F
    SEGPTLNG       0003 0F
    SEGPTOM        0003 0SEGSTAT
    SEGPTUNS       0003 06
    SEGPTUNT       0003 40
    SEGPXDSP       0003 0A
    SEGPXPTL       0003 10
    SEGSHIFT       0003 14
    SEGSTAT        0003

This information is based on z/VM V5R2.0. Last updated on 27 Sep 2006 at 09:24:22 EDT.
Copyright IBM Corporation, 1990, 2005