
48
2.6.5
Notes on Use of Bit-Manipulation Instructions
The BSET, BCLR, BNOT, BST, and BIST instructions read a byte of data, carry out bit
manipulation, then write back the byte of data. Caution is therefore required when using these
instructions on a register containing write-only bits, or a port.
The BCLR instruction can be used to clear internal I/O register flags to 0. In this case, the relevant
flag need not be read beforehand if it is clear that it has been set to 1 in an interrupt handling
routine, etc.
2.7
Addressing Modes and Effective Address Calculation
2.7.1
Addressing Mode
The CPU supports the eight addressing modes listed in table 2-4. 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 2-4
Addressing Modes
No.
Addressing Mode
Symbol
1
Register direct
Rn
2
Register indirect
@ERn
3
Register indirect with displacement
@(d:16,ERn)/@(d:32,ERn)
4
Register indirect with post-increment
Register indirect with pre-decrement
@ERn+
@–ERn
5
Absolute address
@aa:8/@aa:16/@aa:24/@aa:32
6
Immediate
#xx:8/#xx:16/#xx:32
7
Program-counter relative
@(d:8,PC)/@(d:16,PC)
8
Memory indirect
@@aa:8
(1) Register Direct—Rn: The register field of the instruction specifies an 8-, 16-, or 32-bit
general 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.