Rainbow Electronics AT89C2051 - Manual (Page 9)

Microcontroller
5-55
Table 3. Memory Addressing Instructions
Notes: 1. ACC always contains 16 valid bits. All operations are performed in 16-bit precision. 8-bit operands are zero-filled when they
are fetched.
2. SI decrements when data is pushed
3. Data is stored in little endian format.
4. There are no user accessible flags. In the case of CMP, internal flags are maintaned only long enough to accommoate the
LT-UGE instruction.
Name Description (Unused Address Modes)
LD Load ACC 16 bits
LDB Load ACC 8 bits
ADD Add 16 bits
ADDB Add 8 bits
SUB Subtract 16 bits
SUBB Subtract 8 bits
MUL Multiply by 16 bits
MULB Multiply by 8 bits
DIV Divide by 16 bits
DIVB Divide by 8 bits
AND And 16 bits
ANDB And 8 bits
OR OR 16 bits
ORB OR 8 bits
XOR XOR 16 bits
XORB XOR 8 bits
CMP Compare 16 bits (ACC = 1 if equal)
CMPB Compare 8 bits
LDI Load INDEX (16 bits only)
LEAI Load INDEX with address (00, 05)
ST Store ACC 16 bits (00, 05)
STB Store ACC 8 bits (00, 05)
STI Store INDEX (16 bits only) (00, 05)
SHR Shift right (8-bit count only)
SHL Shift left (8-bit count only)