Rainbow Electronics AT89C2051 - Manual (Page 8)

Microcontroller
5-54
Appendix A — Virtual Machine Architecture
Table 1. Fundamental Resource Set
Table 2. General Addressing Modes
Notes: 1. Addressing mode is in lower 3 bits of op code.
2. Mode S+ always pops 16 bits from stack. Only 16-bit values can be pushed.
3. Modes [S+] and [S] will always use a 16-bit address on the top pf the stack but the final target can be 8 or 16 bits.
ACC 16-bit accumulator 8-bit accesses are auto zero-filled
INDEX 16-bit addressing register, cannot be manipulated as 8 bits
SP 16-bit stack pointer
PC 16-bit program counter
Syntax Coding Description
#n x0 ii(ii) Immediate (8 or 16-bit operand)
aaaa x1 dd dd Direct memory address
I x2 Indirect (through INDEX register) no offset
n,I x3 oo Indirect (through INDEX register) with 8-bit offset
n,S x4 oo Indirect (through SP) with 8-bit offset
S+ x5 On Top of Stack (remove)
[S+] x6 Indirect through TOS (remove)
[S] x7 Indirect through TOS (leave on stack)