Programming Interface Information:
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SEG39
Control Block Contents
SEG39 DSECT
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
Copyright IBM Corporation, 1990, 2002