HCS12 datasheet(31/452 Pages) FREESCALE

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S12CPUV2 Reference Manual, Rev. 4.0

Freescale Semiconductor

3.4 Inherent Addressing Mode

Instructions that use this addressing mode either have no operands or all

operands are in internal CPU registers. In either case, the CPU does not

need to access any memory locations to complete the instruction.

Examples:

NOP

;this instruction has no operands

INX

;operand is a CPU register

3.5 Immediate Addressing Mode

Operands for immediate mode instructions are included in the instruction

stream and are fetched into the instruction queue one 16-bit word at a time

during normal program fetch cycles. Since program data is read into the

instruction queue several cycles before it is needed, when an immediate

addressing mode operand is called for by an instruction, it is already present

in the instruction queue.

The pound symbol (#) is used to indicate an immediate addressing mode

operand. One common programming error is to accidentally omit the #

symbol. This causes the assembler to misinterpret the expression that

follows it as an address rather than explicitly provided data. For example,

LDAA #$55 means to load the immediate value $55 into the A accumulator,

while LDAA $55 means to load the value from address $0055 into the A

accumulator. Without the # symbol, the instruction is erroneously

interpreted as a direct addressing mode instruction.

Examples:

LDAA

#$55

LDX

#$1234

LDY

#$67

These are common examples of 8-bit and 16-bit immediate addressing

modes. The size of the immediate operand is implied by the instruction

context. In the third example, the instruction implies a 16-bit immediate

value but only an 8-bit value is supplied. In this case the assembler will

generate the 16-bit value $0067 because the CPU expects a 16-bit value in

the instruction stream.

Example:

BRSET

FOO,#$03,THERE

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