Fujitsu F2MCTM-16LX

CHAPTER 2 CPU

2.8 Register Bank

A register bank consists of eight words. The register bank can be used as the following

general-purpose registers for arithmetic operations: byte registers R0 to R7, word

registers RW0 to RW7, and long word registers RL0 to RL3. In addition, the register

bank can be used as instruction pointers.

RL0 to RL3 are used as the linear pointer that directly accesses entire space.

■Register Bank

Table 2.8-1 lists the functions of the registers. Table 2.8-2 indicates the relationship between the registers.

In the same manner as for an ordinary RAM area, the register bank values are not initialized by a reset. The

status before a reset is maintained. When the power is turned on, however, the register bank will have an

undefined value.

●Direct page register (DPR) <Initial value: 01H>

DPR specifies addr8 to addr15 of the instruction operands in direct addressing mode as shown in Figure

Table 2.8-1 Register Functions

R0 to R7 Used as operands of instructions.

Note: R0 is used as a counter for barrel shift and normalization instructions.

RW0 to RW 7 Used as pointers.

Used as operands of instructions.

Note: RW0 is used as a counter for string instructions.

RL0 to RL3 Used as long pointers.

Used as operands of instructions.

Table 2.8-2 Relationship between Registers

RW0 RL0

RW1

RW2 RL1

RW3

R0 RW4

RL2

R2 RW5

R4 RW6

RL3

R6 RW7