MC68HC705P9 Datasheet, PDF (54/160 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Central Processor Unit (CPU)
4.7.2.2 Read-Modify-Write Instructions
These instructions read a memory location or a register, modify its
contents, and write the modified value back to the memory location or to
the register.
NOTE: Do not use read-modify-write operations on write-only registers.
Table 4-2. Read-Modify-Write Instructions
Instruction
Mnemonic
Arithmetic Shift Left (Same as LSL)
ASL
Arithmetic Shift Right
ASR
Bit Clear
BCLR⁽¹⁾
Bit Set
BSET⁽¹⁾
Clear Register
CLR
Complement (One’s Complement)
COM
Decrement
DEC
Increment
INC
Logical Shift Left (Same as ASL)
LSL
Logical Shift Right
LSR
Negate (Two’s Complement)
NEG
Rotate Left through Carry Bit
ROL
Rotate Right through Carry Bit
ROR
Test for Negative or Zero
TST⁽²⁾
1. Unlike other read-modify-write instructions, BCLR and BSET
use only direct addressing.
2. TST is an exception to the read-modify-write sequence because
it does not write a replacement value.
Technical Data
54
Central Processor Unit (CPU)
For More Information On This Product,
Go to: www.freescale.com
MC68HC705P9 — Rev. 4.0
MOTOROLA