H8SLASH3003 datasheet(59/715 Pages) RENESAS

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2.6.5 Notes on Use of Bit Manipulation Instructions

The BSET, BCLR, BNOT, BST, and BIST instructions read a byte of data, modify a bit in the

byte, then write the byte back. Care is required when these instructions are used to access registers

with write-only bits, or to access ports.

The BCLR instruction can be used to clear flags in the on-chip registers. In an interrupt-handling

routine, for example, if it is known that the flag is set to 1, it is not necessary to read the flag ahead

of time.

2.7 Addressing Modes and Effective Address Calculation

2.7.1 Addressing Modes

The H8/300H CPU supports the eight addressing modes listed in table 2-11. Each instruction uses

a subset of these addressing modes. Arithmetic and logic instructions can use the register direct

and immediate modes. Data transfer instructions can use all addressing modes except program-

counter relative and memory indirect. Bit manipulation instructions use register direct, register

indirect, or absolute (@aa:8) addressing mode to specify an operand, and register direct (BSET,

BCLR, BNOT, and BTST instructions) or immediate (3-bit) addressing mode to specify a bit

number in the operand.

Table 2-11 Addressing Modes

No.

Addressing Mode

Symbol

@ERn

@(d:16, ERn)/@d:24, ERn)

@ERn+

@–ERn

Absolute address

@aa:8/@aa:16/@aa:24

Immediate

#xx:8/#xx:16/#xx:32

Program-counter relative

@(d:8, PC)/@(d:16, PC)

Memory indirect

@@aa:8

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