HCS12 datasheet(43/452 Pages) FREESCALE

43 / 452 page

S12CPUV2 Reference Manual, Rev. 4.0

Freescale Semiconductor

Example:

1000

18 09 C2 20 00

MOVB

$2000 2,PC

Moves a byte of data from $2000 to $1009

The expected location of the PC = $1005. The offset = +2.

[1005 + 2 (for 2,PC) + 2 (for correction) = 1009]

$18 is the page pre-byte, 09 is the MOVB opcode for ext-idx, C2 is the

indexed postbyte for 2,PC (without correction).

The Freescale MCUasm assembler produces corrected object code for

PC-relative moves (18 09 C0 20 00 for the example shown).

NOTE:

Instead of assembling the 2,PC as C2, the correction has been applied to

make it C0. Check whether an assembler makes the correction before using

PC-relative moves.

On the newer HCS12, the instruction queue was implemented such that an

internal pointer, to the start of the next instruction, is always available. On

the HCS12, PC-relative move instructions work as expected without any

offset adjustment. Although this is different from the original M68HC12, it is

unlikely to be a problem because PC-relative indexing is rarely, if ever, used

with move instructions.

3.10.2 Bit Manipulation Instructions

Bit manipulation instructions use either a combination of two or a

combination of three addressing modes.

The clear bits in memory (BCLR) and set bits in memory (BSET) instructions

use an 8-bit mask to determine which bits in a memory byte are to be

changed. The mask must be supplied with the instruction as an immediate

mode value. The memory location to be modified can be specified by means

of direct, extended, or indexed addressing modes.

The branch if bits cleared (BRCLR) and branch if bits set (BRSET)

instructions use an 8-bit mask to test the states of bits in a memory byte. The

mask is supplied with the instruction as an immediate mode value. The

memory location to be tested is specified by means of direct, extended, or

indexed addressing modes. Relative addressing mode is used to determine

the branch address. A signed 8-bit offset must be supplied with the

instruction.

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