MC68HC705J2 Datasheet, PDF (57/82 Pages) Freescale Semiconductor, Inc – member of the low-cost

Freescale Semiconductor, Inc.
10.2.2 Read-Modify-Write Instructions
These instructions read a memory location or a register, modify its contents, and
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write the modified value back to the memory location or to the register. The test for
negative or zero instruction (TST) is an exception to the read-modify-write
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sequence because it does not write a replacement value. Table 10-2 lists the
read-modify-write instructions.
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Table 10-2. Read-Modify-Write Instructions
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Instruction
Arithmetic Shift Left
Arithmetic Shift Right
Clear Bit in Memory
Set Bit in Memory
Clear
Complement (One’s Complement)
Decrement
Increment
Logical Shift Left
Logical Shift Right
Negate (Two’s Complement)
Rotate Left through Carry Bit
Rotate Right through Carry Bit
Test for Negative or Zero
Mnemonic
ASL
ASR
BCLR
BSET
CLR
COM
DEC
INC
LSL
LSR
NEG
ROL
ROR
TST
5
6
7
8
9
10
11
12
13
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10.2.3 Jump/Branch Instructions
Jump instructions allow the CPU to interrupt the normal sequence of the program
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counter. The unconditional jump instruction (JMP) and the jump to subroutine
instruction (JSR) have no register operand. Branch instructions allow the CPU to
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interrupt the normal sequence of the program counter when a test condition is met.
If the test condition is not met, the branch is not performed. All branch instructions
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use relative addressing.
Bit test and branch instructions cause a branch based on the state of any readable
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bit in the first 256 memory locations. These three-byte instructions use a
combination of direct addressing and relative addressing. The direct address of the
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byte to be tested is in the byte following the opcode. The third byte is the signed
offset byte. The CPU finds the conditional branch destination by adding the third
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byte to the program counter if the specified bit tests true. The bit to be tested and
Rev. 2
INSTRUCTION SET
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