Chapter
3.
Instruction Set
ACI
ADC
3-2
ADD
IMMEDIATE
WITH
CARRY
ACI
adds the contents of the second instruction byte and the carry bit
to
the contents of the accumulator and
stores the result
in
the accumulator.
Opcode Operand
ACI
data
The operand specifies the actual data to
be
added to the accumulator except, of course, for the carry bit. Data
may
be
in
the form of a number, an ASCII constant, the label of a previously defined value, or an expression.
The data may not exceed one byte.
The assembler's relocation feature treats
all
e)(ternal and relocatable symbols
as
16-bit addresses. When one of
these symbols appears
in
the operand expression of an immediate instruction, it must
be
preceded
by
either the
HIGH or
LOW
operator to specify which byte of the address
is
to
be
used
in
the evaluation of the expression.
When
neither operator
is
present, the
assembl~r
assumes the
LOW
operator and issues an error message.
Example:
~_o
__
~o
~
data
Cycles:
States:
Addressing:
Flags:
2
7
immediate
Z,S,P,CY,AC
Assume
that
the accumulator contains the value 14H and
that
the carry bit
is
set to one. The instruction
ACI
66
has the following effect:
Accumulator
= 14H
Immediate data = 42H
Carry
00010100
01000010
1
01010111 57H
ADD
WITH
CARRY
The ADC instruction adds one byte
of
data
~Ius
the setting
of
the carry
flag
to
the contents
of
the accumulator.
The result
is
stored
in
the accumulator.
ADC
then updates the setting of the carry flag to indicate the outcome
of
the operation.
The ADC instruction's
use
of the carry bit enables the program to add multi-byte numeric strings.
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