IBM 5150 - Operand Summary; Second Instruction Byte Summary

Operand Summary
"reg field Bit Assignments:
16-Bit[w= 1J
8-Bit [w=OJ
Segment
000 AX 000 AL
00 ES
001 CX
001 CL
01 CS
010 OX 010 OL
10 SS
011
BX
011
BL 11 OS
100 SP 100
AH
101
BP
101 CH
110
SI
110 OH
111 01 111 BH
Second Instruction Byte Summary
I mod I xxx rim
mod Displacement
00 OISP = 0*, disp-Iow and disp-high are absent
01 OISP =disp-Iow sign-extended to 15-bits, disp-high is absent
10 DISP = disp-high: disp-Iow
11 rim is treated as a "reg" field
MF = Memory format
rim
Operand Address
00 - 32-bit Real
000
(BX) + (SI) + OISP
01 -
32-bit Integer 001
(BX) + (01) + OISP
10 - 54-bit Real 010 (BP) + (SI) + OISP
11 - 54-bit Integer
011
(BP) + (01) + OISP
100 (SI) + OISP
101
(01) + DISP
110
(BP) + OISP*
111 (BX)
+ OISP
OISP
follows 2nd byte of instruction (before data if required).
*except if mod = 00 and rim = 110 then EA =disp-high: disp-Iow.
6-4 Instruction Set