MOTOROLA
4-4
DATA TYPES AND ADDRESSING MODES
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CPU16
REFERENCE MANUAL
All modes generate ADDR[15:0]. This address is combined with ADDR[19:16] from an
operand or an extension field to form a 20-bit effective address.
Note
Bank switching is transparent to most instructions. ADDR[19:16] of
the effective address are changed to make an access across a page
boundary. However, extension field values do not change as a result
of effective address computation.
4.3.1 Immediate Addressing Modes
In the immediate modes, an argument is contained in a byte or word immediately fol-
lowing the instruction. For IMM8 and IMM16 modes, the effective address is the ad-
dress of the argument.
There are three specialized forms of IMM8 addressing.
The AIS, AIX/Y/Z, ADDD and ADDE instructions decrease execution time by sign-
extending the 8-bit immediate operand to 16 bits, then adding it to an appropriate
register.
The MAC and RMAC instructions use an 8-bit immediate operand to specify two
signed 4-bit index register offsets.
The PSHM and PULM instructions use an 8-bit immediate operand to indicate
which registers must be pushed to or pulled from the stack.
Table 4-1 Addressing Modes
Addressing
Type
Accumulator Offset
Mode
Mnemonic
E, X
E, Y
E, Z
EXT
EXT20
IMM8
IMM16
IND8, X
IND8, Y
IND8, Z
IND16, X
IND16, Y
IND16, Z
IND20, X
IND20, Y
IND20, Z
INH
IXP
Description
Index Register X with Accumulator E offset
Index Register Y with Accumulator E offset
Index Register Z with Accumulator E offset
Extended
20-bit Extended
8-bit Immediate
16-bit Immediate
Index Register X with unsigned 8-bit offset
Index Register Y with unsigned 8-bit offset
Index Register Z with unsigned 8-bit offset
Index Register X with signed 16-bit offset
Index Register Y with signed 16-bit offset
Index Register Z with signed 16-bit offset
Index Register X with signed 20-bit offset
Index Register Y with signed 20-bit offset
Index Register Z with signed 20-bit offset
Inherent
Signed 8-bit offset added to Index Register X
after effective address is used
8-bit relative
16-bit relative
Extended
Immediate
Indexed 8-Bit
Indexed 16-Bit
Indexed 20-Bit
Inherent
Post-modified Index
Relative
REL8
REL16
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