Technical data

MC68HC912B32 MOTOROLA
MC68HC912B32TS/D 7
2.2 Data Types
The CPU12 supports the following data types:
• Bit data
• 8-bit and 16-bit signed and unsigned integers
• 16-bit unsigned fractions
• 16-bit addresses
A byte is eight bits wide and can be accessed at any byte location. A word is composed of two consec-
utive bytes with the most significant byte at the lower value address. There are no special requirements
for alignment of instructions or operands.
2.3 Addressing Modes
Addressing modes determine how the CPU accesses memory locations to be operated upon. The
CPU12 includes all of the addressing modes of the M68HC11 CPU as well as several new forms of in-
dexed addressing. Table 2 is a summary of the available addressing modes.
Table 2 M68HC12 Addressing Mode Summary
Addressing Mode Source Format Abbreviation Description
Inherent
INST
(no externally supplied
operands)
INH Operands (if any) are in CPU registers
Immediate
INST #
opr8i
or
INST #
opr16i
IMM
Operand is included in instruction stream
8- or 16-bit size implied by context
Direct INST
opr8a DIR
Operand is the lower 8-bits of an address in the
range $0000 – $00FF
Extended INST
opr16a EXT Operand is a 16-bit address
Relative
INST
rel8
or
INST
rel16
REL
An 8-bit or 16-bit relative offset from the current
pc is supplied in the instruction
Indexed
(5-bit offset)
INST
oprx5 , xysp IDX 5-bit signed constant offset from x, y, sp, or pc
Indexed
(auto pre-decrement)
INST
oprx3 , –xys IDX Auto pre-decrement x, y, or sp by 1 ~ 8
Indexed
(auto pre-increment)
INST
oprx3,+xys IDX Auto pre-increment x, y, or sp by 1 ~ 8
Indexed
(auto post-
decrement)
INST
oprx3 , xys– IDX Auto post-decrement x, y, or sp by 1 ~ 8
Indexed
(auto post-increment)
INST
oprx3 , xys+ IDX Auto post-increment x, y, or sp by 1 ~ 8
Indexed
(accumulator offset)
INST
abd , xysp IDX
Indexed with 8-bit (A or B) or 16-bit (D) accumu-
lator offset from x, y, sp, or pc
Indexed
(9-bit offset)
INST
oprx9 , xysp IDX1
9-bit signed constant offset from x, y, sp, or pc
(lower 8-bits of offset in one extension byte)
Indexed
(16-bit offset)
INST
oprx16 , xysp IDX2
16-bit constant offset from x, y, sp, or pc
(16-bit offset in two extension bytes)
Indexed-Indirect
(16-bit offset)
INST [
oprx16 , xysp ] [IDX2]
Pointer to operand is found at...
16-bit constant offset from x, y, sp, or pc
(16-bit offset in two extension bytes)
Indexed-Indirect
(D accumulator
offset)
INST [D,
xysp ] [D,IDX]
Pointer to operand is found at...
x, y, sp, or pc plus the value in D