Addressing

There are various addressing modes available.

Normal addressing

4 bit addressing mode

Only used for addressing the 16 working registers. This is the fastest and smallest addressing mode.

8 bit addressing mode

With this mode you can address 256 memory locations. When addressing registers you can only access the first 256 registers.

12 bit addressing mode

Also called Extended Addressing. Not all instructions support Extended Addressing. Sometimes there is a separate instruction that does the same, but CAN use Extended Addressing. These instructions generally end with an X. An example is LD and LDX. With LDX you can use more addressing modes than with LD.

Special addressing:

Relative addressing

Used for relative jumps. Uses 8 bit signed addresses. You can jump -128 to +127 places from the current PC address. Also used for some other instructions for an offset from a RAM location. More details about that in a bit.

Indirect addressing

In this case an address to a memory location is stored in a register. You pass on the address of the register where the address is stored in to the cpu. Indirect Addresses have an @ prefix. A different term for Indirect Address is Pointer (because the address stored in the register points to another memory location.)


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