Data processing apparatus

A data processing apparatus which executes a program including an instruction which indicates an address for taking out an operand from a main memory in a predetermined addressing mode, said apparatus comprising:

• address generating means for shifting leftwardly by a predetermined number of bits a displacement value of an address which is indicated by the instruction;
• and
• adding means for adding the thus-shifted displacement value to a base value stored in a predetermined register other than a program counter to generate an effective address, when the operand of said instruction is taken out from said main memory, wherein the operand of said instruction taken out from said main memory includes data and not an instruction code.

A microprocessor which executes a program including an instruction which indicates an address for taking out an operand from a main memory in a predetermined addressing mode, said microprocessor comprising:

• a shifting unit which shifts leftwardly by a predetermined number of bits a value of a displacement which is indicated by the instruction and outputs a predetermined number of displacement bits;
• and
• an adder that adds all of the predetermined number of displacement bits output by said shifting unit to a base value stored in a predetermined register other than a program counter and thus generates an effective address, when the operand of said instruction is taken out from said main memory, wherein the operand of said instruction taken out from said main memory includes data and not an instruction code.

A microprocessor which executes a program including an instruction which indicates an address for taking out an operand from a main memory in a predetermined addressing mode, said microprocessor comprising:

• an address generating portion which shifts leftwardly by a predetermined number of bits a displacement value of an address which is indicated by the instruction;
• and
• adding circuitry for adding the thus-shifted displacement value to a base value stored in a predetermined register other than a program counter to generate an effective address, when the operand of said instruction is taken out from said main memory, wherein the operand of said instruction taken out from said main memory includes data and not an instruction code.

A data processing method which executes a program including an instruction which indicates an address for taking out an operand from a main memory in a predetermined addressing mode, said method comprising steps of:

• shifting leftwardly by a predetermined number of bits a value of a displacement which is indicated by the instruction and outputting a predetermined number of displacement bits;
• and
• adding all of the predetermined number of displacement bits output by the shifting step to a base value stored in a predetermined register other than a program counter and thus generating an effective address, when the operand of the instruction is taken out from the main memory, wherein the operand of said instruction taken out from said main memory includes data and not an instruction code.

A data processing method which executes a program including an instruction which indicates an address for taking out an operand from a main memory in a predetermined addressing mode, said method comprising steps of:

• shifting leftwardly by a predetermined number of bits a displacement value of an address which is indicated by the instruction;
• and
• adding the thus-shifted displacement value to a base value stored in a predetermined register other than a program counter to generate an effective address, when the operand of the instruction is taken out from the main memory, wherein the operand of said instruction taken out from said main memory includes data and not an instruction code.