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OSCILLATOR

MBC951

PORT 0

FLIP-FLOPS

PORT 0

BUFFER

8

HIGHER

PROGRAM

COUNTER

LOWER

PROGRAM

COUNTER

PROGRAM

STATUS

WORD

MEMORY

BANK

FLIP-FLOPS

RESIDENT ROM

1 kbyte

(PCF84C12A)

2 kbytes

(PCF84C22A)

4 kbytes

(PCF84C42A)

DECODE

5

888

8

P0.7 to P0.0

RAM

ADDRESS

REGISTER

(8)

ACCUMULATOR

TEMPORARY

REGISTER 1

TEMPORARY

REGISTER 2

ARITHMETIC

LOGIC UNIT

INSTRUCTION

REGISTER

&

DECODER

DECIMAL

ADJUST

CONTROL & TIMING

XTAL 2

XTAL 1

RESET

INT / T0

STOP

IDLE

INTERRUPT

INITIALIZE

CONDITIONAL

BRANCH

LOGIC

INT / T0

TEST 1

TIMER

FLAG

CARRY

ACC

ACC BIT

TEST

RESIDENT RAM ARRAY

64 bytes

MULTIPLEXER

8 LEVEL STACK

(VARIABLE LENGTH)

OPTIONAL SECOND

REGISTER BANK

DATA STORE

D

E

C

O

D

E

REGISTER 0

REGISTER 1

REGISTER 2

REGISTER 3

REGISTER 4

REGISTER 5

REGISTER 6

REGISTER 7

PORT 1

FLIP-FLOPS

PORT 1

BUFFER

P1.0 to P1.4

5

3

TIMER/

EVENT

COUNTER

32

INTERNAL

CLOCK

FREQ.

30

TEST 1

88

8

8

8

INTERRUPT

LOGIC

timer interrupt

external interrupt

Fig.1 Block diagram of PCF84C12A.