Fujitsu CM71-00101-5E User Manual
15
CHAPTER 3 REGISTER DESCRIPTIONS
3.2
General-purpose Registers
The FR family CPU uses general-purpose registers to hold the results of various
calculations, as well as information about addresses to be used as pointers for memory
access. These registers also have special functions with certain types of instructions.
calculations, as well as information about addresses to be used as pointers for memory
access. These registers also have special functions with certain types of instructions.
■
Overview of General-purpose Registers
The FR family CPU has sixteen (16) general-purpose registers each 32 bits in length. Normal instructions
can use any of these sixteen registers without distinction.
Figure 3.2-1 shows the configuration of a general-purpose register.
Figure 3.2-1 General-purpose Register Configuration
■
Special Uses of General-purpose Registers
In addition to functioning as general-purpose registers, "R13", "R14", and "R15" have the following special
uses with certain types of instructions.
●
R13 (Accumulator: AC)
•
Base address register for load/store to memory instructions
[Example: LD @(R13, Rj), Ri]
[Example: LD @(R13, Rj), Ri]
•
Accumulator for direct address designation
[Example: DMOV @dir10,R13]
[Example: DMOV @dir10,R13]
•
Memory pointer for direct address designation
[Example: DMOV @dir10, @R13+]
[Example: DMOV @dir10, @R13+]
32 bits
R0
R1
R2
R3
R12
R13
R14
R15
00000000
H
Initial value
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Accumulator(AC)
Frame pointer(FP)
SSP or USP