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MLC0xxB Series Technical Summary

MEGAWIN

Function Description

Registers

A

Y

X

P

PCH

PCL

1

S

Accumulator

The accumulator is a general-purpose 8-bit register, which stores the results of most arithmetic and

logic operations. In addition, the accumulator usually contains one of two data words, which are used

in these operations.

Index Register (X, Y)

There are two 8-bit index registers (X and Y), which may be used to count program steps or to provide

an index value to be used in generating an effective address. When executing an instruction, which

specifies indexed addressing, the CPU fetches the OP Code and the base address, and modifies the

address by adding the index register to it prior to performing the desired operation. Pre- or post-index

of index address is possible.

Processor Status Register (P)

The 8-bit processor status register contains seven status flags. Some of the flags are controlled by

the program, others may be controlled both the program and the CPU.

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

N

V

1

B

D

I

Z

C

N: Signed flag, 1 = negative, 0 = positive

V: Overflow flag, 1 = true, 0 = false

B: BRK interrupt command, 1 = BRK, 0 = IRQB

D: Decimal mode, 1 = true, 0 = false

I: IRQB disable flag, 1 = disable, 0 = enable

Z: Zero flag, 1 = true, 0 = false

C: Carry flag, 1 = true, 0 = false