三星指令集

　　OVERVIEW The SAM88RCRI instruction set is designed to support the large register file. It includes a full complement of 8-bit arithmetic and logic operations. There are 41 instructions. No special I/O instructions are necessary because I/O control and data registers are mapped directly into the register file. Flexible instructions for bit addressing， rotate， and shift operations complete the powerful data manipulation capabilities of the SAM88RCRI instruction set. REGISTER ADDRESSING To access an individual register， an 8-bit address in the range 0-255 or the 4-bit address of a working register is specified. Paired registers can be used to construct 13-bit program memory or data memory addresses. For detailed information about register addressing， please refer to Chapter 2， “Address Spaces”。 ADDRESSING MODES There are six addressing modes： Register （R）， Indirect Register （IR）， Indexed （X）， Direct （DA）， Relative （RA）， and Immediate （IM）。 For detailed descriptions of these addressing modes， please refer to Chapter 3， “Addressing Modes”。

　　FLAGS REGISTER （FLAGS） The flags register FLAGS contains eight bits that describe the current status of CPU operations. Four of these bits， FLAGS.4–FLAGS.7， can be tested and used with conditional jump instructions; FLAGS register can be set or reset by instructions as long as its outcome does not affect the flags， such as， Load instruction. Logical and Arithmetic instructions such as， AND， OR， XOR， ADD， and SUB can affect the Flags register. For example， the AND instruction updates the Zero， Sign and Overflow flags based on the outcome of the AND instruction. If the AND instruction uses the Flags register as the destination， then simultaneously， two write will occur to the Flags register producing an unpredictable result.