
ST72321xx-Auto Instruction set
Doc ID 13829 Rev 1 179/243
18.1.2 Immediate
Immediate instructions have 2 bytes. The first byte contains the opcode and the second byte
contains the operand value.
18.1.3 Direct
In Direct instructions, the operands are referenced by their memory address.
The direct addressing mode consists of two submodes:
Direct (short)
The address is a byte, thus requires only one byte after the opcode, but only allows 00 - FF
addressing space.
Direct (long)
The address is a word, thus allowing 64 Kbyte addressing space, but requires 2 bytes after
the opcode.
18.1.4 Indexed (no offset, short, long)
In this mode, the operand is referenced by its memory address, which is defined by the
unsigned addition of an index register (X or Y) with an offset.
The indexed addressing mode consists of three submodes:
Indexed (no offset)
There is no offset, (no extra byte after the opcode), and allows 00 - FF addressing space.
Indexed (short)
The offset is a byte, thus requires only one byte after the opcode and allows 00 - 1FE
addressing space.
Indexed (long)
The offset is a word, thus allowing 64 Kbyte addressing space and requires 2 bytes after the
opcode.
Table 99. Immediate instructions
Instruction Function
LD Load
CP Compare
BCP Bit Compare
AND, OR, XOR Logical Operations
ADC, ADD, SUB, SBC Arithmetic Operations
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