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When the instruction at 5000 is executed, the
rightmost byte of register 1 is ORed with the
second byte of the target instruction:
Register byte:
Instruction byte:
Result:
0000 00002
0000 00112
0000 00112
00
03
03
causing the instruction at 3820 to be executed as if
it originally were:
Machine Format
Op Code
L
02
03
o
1 0001
Assembler Format
Op Code
01(1,B1),02(B2)
MVC
3(4,12),0(13)
However, after execution:
Register 1 is unchanged.
The instruction at 3820 is unchanged.
The contents of the four bytes starting at location 90AO
have been moved to the four bytes starting at location
8916.
The CPU next executes the instruction at address 5004
(PSW bits 40-63 contain 00 50 04).
INSERT CHARACTERS UNDER MASK
(ICM)
The INSERT CHARACTERS UNDER MASK
(ICM) instruction may be used to replace all or
selected bytes in a general register with bytes from
storage ·and to set the condition code to indicate
the value· of the inserted field.
For example,.if it is desired to insert a three-byte
address from FIELDA into register 5 and leave the
leftmost byte of the register unchanged, assume:
Machine Format
Op Code
BF
5
7
* * * *
Assembler Format
ICM
5, B 10111
I
,F I E L OA
FIELOA:
Register 5 (before):
Register 5 (after):
Condition code (after):
As another example:
Machine Format
FE DC BA
12 34
56 78
12 FE DC BA
1
(leftmost bit
of inserted
field is one)
BF
6
9
* * * *
Assembler Format
ICM
6,
B
I
1001
I
,F I ELOB
FIELOB:
Register
6
(before):
Register
6
(after):
Condition code (after):
12 34
00 00 00 00
12 00 00 34
2
(inserted field
is nonzero
with leftmost
zero bit)
When the mask field contains 1111, the ICM
instruction produces the same result as LOAD (L)
(provided that the indexing capability of the RX
format is not needed), except that ICM alt;o sets
the condition code. The condition-code setting is
useful when an all-zero field (condition code
0)
or
a leftmost one bit (condition code
1)
is used as a
flag.
LOAD (L, LR)
The LOAD instructions take four bytes from
storage or from a general register and place them
unchanged into a general register. For example,
assume that the four bytes starting with location
21003 are to be loaded into register 10. Initially:
Register 5 contains 00 02 00 00.
Register 6 contains 00 00 10 03.
The contents of register 10 are not significant.
Storage locations 21003-21006 contain 00 00 AB CD.
To load register 10, the RX form of the
instruction can be used:
Machine Format
Op Code
58
A
5
6
I
0001
Appendix A. Number Representation and Instruction-Use Examples
A-1S
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