How about addressing modes?

·      There are 8 addressing modes. The addressing modes determine how the operand byte is selected.

·      The direct and indirect addressing modes are used to distinguished the SPR space and data memory space

·      The relative instructions are based on the value of the program counter.

 

 

 

Instruction Set summary

 

 

 

 

 

 

 

Indexed addressing- the indexed addressing is useful when there is a need to retrieved data from a loop of table.

Immediate addressing- this mode of addressing uses either an 8 or 16 bit constant value a the source operand.

Indirect addressing- this mode uses a pointer to hold the effective address of the operand.

               -only register R0 R1 and DPTR can be used as the pointer register

Long addressing- it is a 3 bytes instructions and last 2 bytes specify a 16 bit destination location where the program branches.

Absolute addressing- two instructions associated with this mode of addressing are ACALL and JMP instructions.

 

 



 

 

What is Instruction Set?

·         A computer instruction is made up of an operation code (op-code) followed by either zero, one or two bytes of operands.

·         The op code identifies the type of operation to be performed while the operands identify the source and destination of the data.

·         the operands can be :

- The data value itself

- A cpu register

- A memory location

- A I/O port

·         If the instruction is associated with more than one operand the format is always

Instruction Destination, Source