General-Purpose Register (Register Bank) - Fujitsu MB90480 Series Hardware Manual

2.3.7

General-Purpose Register (Register Bank)

This section explains the general-purpose register (register bank) functions.
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General-purpose register (register bank)
A register bank consists of 8 words and is used as a general-purpose register for arithmetic
operation in the byte register (R0 to R7), word register (RW0 to RW7), and long-word register
(RL0 to RL3). A register bank is also used as an instruction pointer. Table 2.3-2 lists the register
functions and Figure 2.3-12 shows the relationship among registers.
Register bank values are not initialized by a reset, the same as for RAM spaces, but the state
before resetting is kept.
At power-on, however, the values are undefined.
Table 2.3-2 Register functions
R0 to R7
RW0 to RW7
RL0 to RL3
R0
R1
R2
R3
Used as operand in different instructions
Note:
R0 is used as the barrel shift counter or normalization instruction counter.
Used as a pointer or operand in different instructions
Note:
RW0 is used as a string instruction counter.
Used as a long pointer or operand in different instructions
Figure 2.3-12 Relationship among registers
RW0 RL0
RW1
RW2 RL1
RW3
RL2
R4 RW6
R5
R6 RW7
R7
CHAPTER 2 CPU
RL3
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