The Discordant Opposition Journal Issue 10 - File 13

eZine lover (@eZine)

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The Discordant Opposition Jour

 · 2 years ago

D|amond's list of 8086 processor (non extended non 32bit) registers 8086 PROCESSOR

-  typ b  nm     lnm                     desc 
1  gen 16 ax ... Accumulator............ arithmetic computations 
2  gen 16 bx ... Base................... indirect addresses 
3  gen 16 cx ... Count.................. counting (iterations in a loop) 
4  gen 16 dx ... Data................... catches arithmetic overflow and 
                                         IO addresses when accessing data 
                                         on the IO bus. 
5  gen 16 si ... Source Index........... processing character signs and 
                                         indirect addressing 
6  gen 16 di ... Destination Index...... processing character signs and 
                                         indirect addressing 
7  gen 16 bp ... Base Pointer........... access parameters and local 
                                         variables in procedures 
8  gen 16 sp ... Stack Pointer.......... maintains the program stack*** 
9      8  al ... ax LO bit ............. ax 
10     8  ah ... ax HO bit ............. ax 
11     8  bl ... bx LO bit ............. bx 
12     8  bh ... bx HO bit ............. bx 
13     8  cl ... cx LO bit ............. cx 
14     8  ch ... cx HO bit ............. cx 
15     8  dl ... dx LO bit ............. dx 
16     8  dh ... dx HO bit ............. dx 
17 seg 16 cs ... Code Segment .......... points at the segment containing 
                                         the currently executing machine 
                                         instructions 
18 seg 16 ds ... Data Segment .......... points at global variables for 
                                         the program 
19 seg 16 es ... Extra Segment ......... an extra segment register (when 
                                         it is difficult or impossible to 
                                         modify the other segment registers, 
                                         use this) 
20 seg 16 ss ... Stack Segment ......... stores important machine state 
                                         information, subroutine return 
                                         addresses, procedure parameters, 
                                         and local variables 
21 spe 16 ip ... Instruction Pointer ... ***contains the address of the 
                                         currently executing instruction 
22 spe N     ... Flags Register ........ ****eclectic collection of one 
                                         bit values which help determine 
                                         the current state of the processor

Segments of memory on the 8086 can be no larger than 65,536 bytes long.

Besides the extra bits in the flags register, the 80286 also has five additional registers used by an operating system to support memory management and multiple processes:

the machine status word (msw), the global descriptor table register (gdtr), the local descriptor table register (ldtr), the interrupt descriptor table register (idtr) and the task register (tr).

Discordia: After segments of memory and before. -pika
hail discordia
EOF