H8S2245 datasheet(92/818 Pages) RENESAS

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Section 2 CPU

Rev.3.00 Mar. 26, 2007 Page 50 of 772

REJ09B0355-0300

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. See section 2.10.3, Bit Manipulation Instructions, for details.

2.7

Addressing Modes and Effective Address Calculation

2.7.1

Addressing Modes

The 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 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:32,ERn)

@ERn+

@–ERn

Absolute address

@aa:8/@aa:16/@aa:24/@aa:32

Immediate

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

Program-counter relative

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

Memory indirect

@@aa:8

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