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