Direct Address Area - Fujitsu FR Family Instruction Manual

2.1.1

Direct Address Area

The lower portion of the address space is used for the direct address area. Instructions
that specify direct addresses allow you to access this area without the use of general-
purpose registers, using only the operand information in the instruction itself. The size
of the address area that can be specified by direct addressing varies according to the
length of the data being transferred.
■ Direct Address Area
The size of the address area that can be specified by direct addressing varies according to the length of the
data being transferred, as follows:
• Transfer of byte data:
• Transfer of half-word data: 0000 0000
• Transfer of word data:
■ Use of Operand Information Contained in Instructions
The 8-bit address information contained in the instruction has the following significance.
• In byte data:
• In half-word data: Value is doubled and used as the lower 9 bits of the address.
• In word data:
Figure 2.1-2 shows the relationship between the length of the data that designates the direct address, and
the actual address in memory.
Figure 2.1-2 Relation between Direct Address Data and Memory Address Value
[Example 1] Byte data: DMOVB R13,@58
Object code:1A58
[Example 2] Half-word data: DMOVH R13,@58
Object code:192C
[Example 3] Word data: DMOV R13,@58
Object code:1816
0000 0000
0000 0000
Value represents the lower 8 bits of the address.
Value is multiplied by 4 and used as the lower 10 bits of the address.
No data shift
H
R13 12345678
Right 1-bit shift
Left 1-bit shift
H
R13 12345678
H
Right 2-bit shift
Left 2-bit shift
H
R13 12345678
CHAPTER 2 MEMORY ARCHITECTURE
to 0000 00FF
H H
to 0000 01FF
H H
to 0000 03FF
H H
H
Memory space
58
H
0000 0058
H
78
H
Memory space
58
H
0000 0058
H
Memory space
58
H
0000 0058
H
5678
1345678
7