MMC2001
INTEGER CPU
MOTOROLA
REFERENCE MANUAL
2-5
2.5 Data Format Summary
The operand data formats supported by the integer unit are standard two’s-comple-
ment data formats. The operand size for each instruction is either explicitly encoded
in the instruction (load/store instructions) or implicitly defined by the instruction opera-
tion (index operations, byte extraction). Typically, instructions operate on all 32 bits of
the source operand(s) and generate a 32-bit result.
Memory is viewed from a big-endian byte ordering perspective. The most significant
byte (byte 0) of word 0 is located at address 0. Bits are numbered within a word start-
ing with bit 31 as the most significant bit.
Figure 2-2 Data Organization in Memory
Figure 2-3 Data Organization in Registers
Byte 0
Byte 1
Byte 2
Byte 3
Word at 0
31
0
Byte 4
Byte 5
Byte 6
Byte 7
Word at 4
Byte 8
Byte 9
Byte A
Byte B
Word at 8
Byte C
Byte D
Byte E
Byte F
Word at C
Byte
Signed Byte
S
S S S S S S S S S S S S S S S S S S S S S S S S
0
8 7
31
Byte
Unsigned Byte
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0
8 7
31
Halfword
Signed
S
S S S S S S S S S S S S S S S S
0
16 15
31
Halfword
Halfword
Unsigned
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0
16
15
31
Halfword
0
31
Word
Byte 3
Byte 2
Byte 1
Byte 0
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