Page 32 - Introduction to Microcontrollers Architecture, Programming, and Interfacing of The Motorola 68HC12
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1,3 A Few Instructions And Some Simple Programs 9
Notice that the "#" is missing in this mnemonic because we are using direct addressing
instead of immediate addressing. Also, the second two bytes of the instruction give the
address of the operand, high byte of the address first.
The store instruction is like the load instruction described earlier except that it works
in the reverse manner (and a STAA or STAB with the immediate addressing mode is
neither sensible nor available). It moves a word from a register in the MPU to a memory
location specified by the effective address. The mnemonic, for store from A, is STAA;
the instruction
STAA 2090
will store the byte in A into location 2090 (decimal). Its machine code is
where we note that the number 2090 is stored in hexadecimal as $082A. With direct
addressing, two bytes are always used to specify the address even though the first byte
may be zero.
Figure 13. Registers and Memory
