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Semiconductor Group
131
Instruction Set
Subtraction
– SUBB (subtract with borrow) subtracts the second source operand from the the first operand
(the accumulator), subtracts one (1) if CY is set and returns the result to A.
– DEC (decrement) subtracts one (1) from the source operand and returns the result to the
operand.
Multiplication
– MUL performs an unsigned multiplication of the A register, returning a double byte result. A
receives the low-order byte, B receives the high-order byte. OV is cleared if the top half of the
result is zero and is set if it is not zero. CY is cleared. AC is unaffected.
Division
– DIV performs an unsigned division of the A register by the B register; it returns the integer
quotient to the A register and returns the fractional remainder to the B register. Division by
zero leaves indeterminate data in registers A and B and sets OV; otherwise, OV is cleared.
CY is cleared. AC remains unaffected.
Flags
Unless otherwise stated in the previous descriptions, the flags of PSW are affected as follows:
– CY is set if the operation causes a carry to or a borrow from the resulting high-order bit;
otherwise CY is cleared.
– AC is set if the operation results in a carry from the low-order four bits of the result (during
addition), or a borrow from the high-order bits to the low-order bits (during subtraction);
otherwise AC is cleared.
– OV is set if the operation results in a carry to the high-order bit of the result but not a carry
from the bit, or vice versa; otherwise OV is cleared. OV is used in two’s-complement
arithmetic, because it is set when the signal result cannot be represented in 8 bits.
– P is set if the modulo-2 sum of the eight bits in the accumulator is 1 (odd parity); otherwise P
is cleared (even parity). When a value is written to the PSW register, the P bit remains
unchanged, as it always reflects the parity of A.
*
Summary of Contents for SAB 80515 Series
Page 9: ...Semiconductor Group 9 Introduction Figure 1 2 Block Diagram ...
Page 12: ...Semiconductor Group 12 Fundamental Structure Figure 2 1 Detailed Block Diagram ...
Page 18: ...Semiconductor Group 18 Central Processing Unit Figure 3 1 Fetch Execute Sequence ...
Page 73: ...Semiconductor Group 73 On Chip Peripheral Components Figure 7 25 A D Converter Block Diagram ...
Page 83: ...Semiconductor Group 83 On Chip Peripheral Components Figure 7 33 a Timer 2 Block Diagram ...
Page 215: ...Device Specifications Semiconductor Group 215 ...
Page 217: ...Device Specifications Semiconductor Group 217 Pin Configuration P LCC 68 ...
Page 219: ...Device Specifications Semiconductor Group 219 Logic Symbol ...
Page 226: ...Device Specifications Semiconductor Group 226 Figure 1 Block Diagram ...
Page 229: ...Device Specifications Semiconductor Group 229 Figure 2 Memory Address Spaces ...
Page 239: ...Device Specifications Semiconductor Group 239 Figure 4 Block Diagram of the A D Converter ...
Page 241: ...Device Specifications Semiconductor Group 241 Figure 5 Interrupt Request Sources ...
Page 242: ...Device Specifications Semiconductor Group 242 Figure 6 Interrupt Priority Level Structure ...