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' Segment table entry is
                                            invalid
              ...1 ....      SEGCOMMN       X'10' Common segment bit
              .... 1111      SEGPTLNG       X'0F' Page table length (in units
                                            of 64 byte blocks, minus 1).
              0SEGSTAT       SEGPTOM        X'7FFFFFC0' Isolate page-table
                                            origin
              ..1. ....      SEGINVM        X'00000020' Isolate invalid bit
              ...1 ....      SEGCOMM        X'00000010' Isolate
                                            common-segment bit
              .... 1111      SEGPTLM        X'0000000F' 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 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 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 Number of bits to shift left in
                                            order to multiply by SEGPTUNT.
              ...1 ....      SEGPXPTL       12+4 Bits to shift right an
                                            isolated page index to obtain a
                                            page- table length.
              .... 1.1.      SEGPXDSP       12-2 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 V4R3.0. Last updated on 30 Apr 2002 at 18:32:35 EDT.
Copyright IBM Corporation, 1990, 2002