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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.
Hex Dec Type/Val Lng Label (dup) Comments
---- ---- --------- ---- -------------- --------
0000 0 Structure SEGG z/Architecture Segment Table Entry
0000 0 Dbl-Word 8 SEGGENTR Segment table entry
00000008 SEGGLEN *-SEGGENTR Length of one STE
0008 8 Dbl-Word 8 SEGGNEXT (0) Next segment table entry
0000 0 Signed 4 SEG64W0 Word 0 of STE Bits 0-31 of PTO
0004 4 Signed 4 SEG64W1 Word 1 of STE
0004 4 Bitstring 1 * (2) Bits 32-47 of PTO
0006 6 Bitstring 1 SEGGSTA2 Bits 48-52 of PTO, plus the
following three bits:
.... ..1. SEGGPROT X'02' SEGGPROT Entire segment is
page protected
0007 7 Bitstring 1 SEGGSTAT Segment Table Entry Status
..1. .... SEGGINVL X'20' SEGGINVL 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' SEGGCOMN Common segment bit
.... 11.. SEGGTTBT X'0C' SEGGTTBT Table Type bits -
must be B'00' 64-bit mask
X'FFFFFFFFFFFFFF800'
SEGGSTAT SEGGPTMH X'FFFFFFFF' SEGGPTMH Isolate
page-table origin - High
SEGGSTAT SEGGPTML X'FFFFF800' SEGGPTML Isolate
page-table origin - Low 64-bit
mask X'FFFFFFFF80000000'
SEGGSTAT SEGG2GMH X'FFFFFFFF' SEGG2GMH Isolate STE
bits which must be zero in a
<2G STE - High
.... .... SEGG2GML X'80000000' SEGG2GML Isolate STE
bits which must be zero in a
<2G STE - Low 64-bit mask
X'0000000000000200' 32-bit high
X'00000000'
SEGGSTAT SEGGPROM X'00000200' SEGGPROM Isolate
segment page protect bit 64-bit
mask X'0000000000000020' 32-bit
high X'00000000'
..1. .... SEGGINVM X'00000020' SEGGINVM Isolate
invalid bit 64-bit mask
X'0000000000000010' 32-bit high
X'00000000'
...1 .... SEGGCOMM X'00000010' SEGGCOMM Isolate
common-segment bit Notes : Since
segment tables may be longer (up
to 16K) than their boundary
alignment (4K), a STO can not be
computed from an STE address via
a mask.
...1 .1.. SEGGSHFT 20 SEGGSHFT Bits to shift by to
convert between segment number
and virtual address.
SEGGSTAT SEGGPTUN 2048 SEGGPTUN Number of bytes in
a page-table. All page tables are
"full" page tables containing 256
8 byte entries, representing 1M
of virtual storage.
.... 1.11 SEGGPTUS 11 SEGGPTUS Number of bits to
shift left in order to multiply
by SEGGPTUN.
.... 1... SEGGPXNUM 8 SEGGPXNUM Number of bits in a
PX
1111 1111 SEGGPXRIT X'FF' SEGGPXRIT Mask to isolate a
right- justified PX
.... 1..1 SEGGPXDS 12-3 SEGGPXDS Bits to shift to
convert between an isolated page
index and the displacement into
the page table of applicable 8
byte PTE.
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