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MAXM
MAX ((A), (M)) ⇒ M
Operation:
Description:
Subtracts an unsigned 8-bit value in memory from an unsigned 8-bit
value in accumulator A to determine which is larger, and leaves the larg-
er of the two values in the memory location. The Z status bit is set when
the result of the subtraction is zero (the values are equal), and the C sta-
tus bit is set when the subtraction requires a borrow (the value in mem-
ory is larger than the value in the accumulator). When C = 0, the value
in accumulator A has replaced the value in memory.
The unsigned value in memory is accessed by means of indexed ad-
dressing modes, which allow a great deal of flexibility in specifying the
address of the operand.
Condition Codes and Boolean Formulas:
S
–
N:
Z:
V:
C:
Condition codes reflect internal subtraction (R = A – M).
Addressing Modes, Machine Code, and Execution Times:
Source Form
MAXM oprx0_xysp
MAXM oprx9,xysp
MAXM oprx16,xysp
MAXM [D ,xysp ]
MAXM [ oprx16,xysp ]
MOTOROLA
6-140
Place Larger of Two
Unsigned 8-Bit Values
in Memory
X
H
I
N
Z
∆
∆
–
–
–
Set if MSB of result is set; cleared otherwise.
Set if result is $00; cleared otherwise.
X7 • M7 • R7 + X7 • M7 • R7
Set if a two's complement overflow resulted from the operation;
cleared otherwise.
X7 • M7 + M7 • R7 + R7 • X7
Set if the value of the content of memory is larger than the value of
the accumulator; cleared otherwise.
Address Mode
IDX
IDX1
IDX2
[D,IDX]
[IDX2]
INSTRUCTION GLOSSARY
V
C
∆
∆
Object Code
18 1C xb
18 1C xb ff
18 1C xb ee ff
18 1C xb
18 1C xb ee ff
MAXM
Cycles
Access Detail
4
OrPw
5
OrPwO
6
OfrPwP
7
OfIfrPw
7
OfIPrPw
CPU12
REFERENCE MANUAL
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