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Instruction Classification
4-29Assembly 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 An imm8
Class 2b 1 1 1 0 0 next A An C2b 0 0 1 A~ ~A
Table 4–17. Class 2a Instruction Description
C2a Mnemonic Description
0 0 0 ADDB An, 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 An, imm8 Load an 8-bit positive constant into accumulator. ALU status is modified.
0 1 0 SUBB An, imm8 Subtract 8-bit positive constant from accumulator and store result
accumulator. ALU status modified.
0 1 1 CMPB An, imm8 Modify ALU status with the result of 8-bit positive value subtracted from
accumulator. Original accumulator value not modified.
1 0 0 ORB An, imm8 Logical OR 8-bit positive constant with accumulator and store result to
accumulator. ALU status modified.
1 0 1 ANDB An, imm8 Logical AND 8-bit positive constant with accumulator. Store result to
accumulator. ALU status modified.
1 1 0 XORB An, 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.