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As a result, PA
DDR is cleared to 0, making PA
0
PA
DDR are set to 1, making PA
6
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
1
Register direct
2
Register indirect
3
Register indirect with displacement
4
Register indirect with post-increment
Register indirect with pre-decrement
5
Absolute address
6
Immediate
7
Program-counter relative
8
Memory indirect
1 Register Direct—Rn: The register field of the instruction code specifies an 8-, 16-, or 32-bit
register containing the operand. R0H to R7H and R0L to R7L can be specified as 8-bit registers.
R0 to R7 and E0 to E7 can be specified as 16-bit registers. ER0 to ER7 can be specified as 32-bit
registers.
2 Register Indirect—@ERn: The register field of the instruction code specifies an address
register (ERn), the lower 24 bits of which contain the address of the operand.
an input pin. In addition, PA
0
and PA
output pins.
7
6
Symbol
Rn
@ERn
@(d:16, ERn)/@d:24, ERn)
@ERn+
@–ERn
@aa:8/@aa:16/@aa:24
#xx:8/#xx:16/#xx:32
@(d:8, PC)/@(d:16, PC)
@@aa:8
DDR and
7
41
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