IBM 4300 Manual page 269

Assembler Format
Op Code R1,D2(X2,B2)
L 10,0(5,6)
After the instruction is executed, register 10
contains 00 00 AB CD.
LOAD ADDRESS (LA)
The LOAD ADDRESS instruction provides a
convenient way to place a nonnegative binary
integer up to 4095
10
in a register without first
defining a constant and then using it as an
operand. For example, the following instruction
places the number 2048
10
in register 1:
Machine Format
Op Code
41
° °
I
800
1
Assembler Format
Op Code R1,D2(X2,B2)
LA 1,2048(0,0)
The LOAD ADDRESS instruction can also be
used to increment a register by an amount up to
4095
10
specified in the D2 field. Only the
rightmost 24 bits of the result are retained,
however. For example, assume that register 5
contains 00 12 34 56.
The instruction:
Machine Format
Op Code R1
41 5
o
5
I
OOAI
Assembler Format
Op Code R1,D2(X2,B2)
LA 5,10(0,5)
adds 10 (decimal) to the contents of register 5 as
follows:
A-16 IBM 4300 Processors Principles of Operation
Register 5 (old): 00 12 34 56
D2 field: 00 00 00 OA
Register 5 (new): 00 12 34 60
The register may be specified as either B2 or X 2 .
Thus, the instruction LA 5,10(5,0) produces the
same result.
As the most general example, the instruction LA
6,10(5,4) adds the displacement, in this case 10, to
the contents of register 4 and to the contents of
register 5 and places the 24-bit sum of these three
values in register 6.
LOAD HALFWORD (LH)
The LOAD HALFWORD instruction places
unchanged a halfword from storage into the right
half of a register. The left half of the register is
loaded with zeros or ones according to the sign
(leftmost bit) of the halfword.
For example, assume that the two bytes in
storage locations 1803-1804 are to be loaded into
register 6. Also assume:
The contents of register 6 are not significant.
Register 14 contains 00 00 18 03.
Locations 1803-1804 contain 00 20.
The iristruction required to load the register is:
Machine Format
48
6
°
E 10001
Assembler Format
Op Code R1,D2(X2,B2)
LH 6,0(0,14)
After the instruction is executed, register 6
contains 00 00 00 20. If locations 1803-1804 had
contained a negative number, for example, A 7 B6,
a minus sign would have been propagated to the
left, giving FF FF A 7 B6 as the final result in
register 6.
MOVE (MVC, MVI)
Move (MVC)
The MOVE (MVC) instruction can be used to
move data from one storage location to another.