General-Purpose Registers - Fujitsu FR Family Instruction Manual

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.
■ 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.
■ 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]
• Accumulator for direct address designation
[Example: DMOV @dir10,R13]
• Memory pointer for direct address designation
[Example: DMOV @dir10, @R13+]
Figure 3.2-1 General-purpose Register Configuration
32 bits
R0
R1
R2
R3
R12
R13
Accumulator(AC)
R14
Frame pointer(FP)
R15
SSP or USP
CHAPTER 3 REGISTER DESCRIPTIONS
Initial value
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
Undefined
00000000
H
15