SAB80515 Datasheet, PDF (137/270 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller Family

Instruction Set
ADD
A, <src-byte>
Function:
Add
Description:
ADD adds the byte variable indicated to the accumulator, leaving the result in the
accumulator. The carry and auxiliary carry flags are set, respectively, if there is a
carry out of bit 7 or bit 3, and cleared otherwise. When adding unsigned integers,
the carry flag indicates an overflow occurred.
OV is set if there is a carry out of bit 6 but not out of bit 7, or a carry out of bit 7 but
not out of bit 6; otherwise OV is cleared. When adding signed integers, OV indicates
a negative number produced as the sum of two positive operands, or a positive sum
from two negative operands.
Four source operand addressing modes are allowed: register, direct, register-
indirect, or immediate.
Example:
The accumulator holds 0C3_H (11000011_B) and register 0 holds 0AA_H (10101010_B).
The instruction
ADD A,R0
will leave 6D_H (01101101_B) in the accumulator with the AC flag cleared and both
the carry flag and OV set to 1.
ADD
A,Rn
Operation:
ADD
(A) ← (A) + (Rn)
Encoding:
Bytes:
Cycles:
0010 1rrr
1
1
ADD
A,direct
Operation:
ADD
(A) ← (A) + (direct)
Encoding:
Bytes:
Cycles:
0010 0101
2
1
direct address
Semiconductor Group
137