Instruction Set; Addressing Modes - Siemens C500 User Manual

4

Instruction Set

The C500 8-bit microcontroller family instruction set includes 111 instructions, 49 of which are
single-byte, 45 two-byte and 17 three-byte instructions. The instruction opcode format consists of a
function mnemonic followed by a Ódestination, sourceÓ operand field. This field specifies the data
type and addressing method(s) to be used.
Like all other members of the 8051-family, the C500 microcontrollers can be programmed with the
same instruction set common to the basic member, the SAB 8051.
Thus, the C500 family microcontrollers are 100% software compatible to the SAB 8051 and may be
programmed with 8051 assembler or high-level languages.
4.1

Addressing Modes

The C500 uses five addressing modes:
Ð register
Ð direct
Ð immediate
Ð register indirect
Ð base register plus index-register indirect
Table 4-1 summarizes the memory spaces which may be accessed by each of the addressing
modes.
Register Addressing
Register addressing accesses the eight working registers (R0 - R7) of the selected register bank.
The least significant bit of the instruction opcode indicates which register is to be used. ACC, B,
DPTR and CY, the Boolean processor accumulator, can also be addressed as registers.
Direct Addressing
Direct addressing is the only method of accessing the special function registers. The lower
128 bytes of internal RAM are also directly addressable.
Immediate Addressing
Immediate addressing allows constants to be part of the instruction in program memory.
Semiconductor Group 4-1
Instruction Set
C500 Family
1998-04-01