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Instruction Classification
4-29
Assembly Language Instructions
constants. Long constants (16 bits) and long string constants differ in that ref-
erences are made to constants in the second word of the two-word instruction
word. References made to a single 16 bit integer constant are immediate. That
is, the actual constant value follows the first word opcode in memory. For string
constants, the second word reference to the constants is immediate-indirect
which indicates that the second word is the address of the least significant
word of the string constant. This definition allows all long string constants to
be located in a table and permits the reference in the machine language listing
to be consistent with those of shorter constants.
Table 4–16. Class 2 Instruction Encoding
Bit 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Class 2a 1 0 1 0 C2a A
n imm8
Class 2b 1 1 1 0 0
next A
A
n
C2b 0 0 1 A~ ~A
Table 4–17. Class 2a Instruction Description
C2a Mnemonic Description
0 0 0 ADDB A
n
,
imm8
Add an 8 bit positive constant to the accumulator and store the result in the
accumulator. ALU status is modified.
0 0 1 MOVB A
n
,
imm8
Load an 8 bit positive constant into accumulator. ALU status is modified.
0 1 0 SUBB A
n
,
imm8
Subtract 8 bit positive constant from accumulator and store result
accumulator. ALU status modified.
0 1 1 CMPB A
n
,
imm8
Modify ALU status with the result of 8 bit positive value subtracted from
accumulator. Original accumulator value not modified.
1 0 0 ORB A
n
,
imm8
Logical OR 8 bit positive constant with accumulator and store result to
accumulator. ALU status modified.
1 0 1 ANDB A
n
,
imm8
Logical AND 8 bit positive constant with accumulator. Store result to
accumulator. ALU status modified.
1 1 0 XORB A
n
,
imm8
Logical XOR 8 bit positive constant with accumulator. Store result to
accumulator. ALU status modified.
1 1 1 MOVB MR,
imm8
Load 8 bit constant to Multiplier register (MR). Does not change UM mode in
status register but will zero fill the top 8 bits in MR register. No change in status.