Siemens C500 User Manual page 28

Table 4-1
Addressing Modes and Associated Memory Spaces
Addressing Modes
Register addressing
Direct addressing
Immediate addressing
Register indirect addressing
Base register plus index register addressing
Register Indirect Addressing
Register indirect addressing uses the contents of either R0 or R1 (in the selected register bank) as
a pointer to locations in a 256-byte block: the 256 bytes of internal RAM or the lower 256 bytes of
external data memory. Note that the special function registers are not accessible by this method.
The upper half of the internal RAM can be accessed by indirect addressing only. Access to the full
64 Kbytes of external data memory address space is accomplished by using the 16-bit data pointer.
Execution of PUSH and POP instructions also uses register indirect addressing. The stack may
reside anywhere in the internal RAM.
Base Register plus Index Register Addressing
Base register plus index register addressing allows a byte to be accessed from program memory
via an indirect move from the location whose address is the sum of a base register (DPTR or PC)
and index register, ACC. This mode facilitates look-up table accesses.
Boolean Processor
The Boolean processor is a bit processor integrated into the C500 family microcontrollers. It has its
own instruction set, accumulator (the carry flag), bit-addressable RAM and l/O.
The bit manipulation instructions allow:
Ð set bit
Ð clear bit
Ð complement bit
Ð jump if bit is set
Ð jump if bit is not set
Ð jump if bit is set and clear bit
Ð move bit from / to carry
Addressable bits, or their complements, may be logically AND-ed or OR-ed with the contents of the
carry flag. The result is returned to the carry register.
Semiconductor Group
Associated Memory Spaces
R0 through R7 of selected register bank, ACC,
B, CY (Bit), DPTR
Lower 128 bytes of internal RAM, special
function registers
Program memory
Internal RAM (@R1, @R0, SP), external data
memory (@R1, @R0, @DPTR)
Program memory (@A + DPTR, @A + PC)
4-2
Instruction Set
C500 Family
1998-04-01