NAD C 720BEE Service Manual page 12

AT89C55WD
KEY BOARD : IC704
RAM ADDR.
RAM
REGISTER
B
ACC
REGISTER
TMP2
TIMING AND INSTRUCTION
CONTROL
REGISTER
WATCH
DOG
OSC
PIN CONFIGURATION
P1.0 ------ P1.7
PORT 0 DRIVERS
PORT 0
LATCH
TMP1
ALU
INTERRUPT,SERIAL PORT
PSW
PORT 1
LATCH
PORT 1 DRIVERS
P1.0 ------ P1.7
- 12 -
P2.0 ------ P2.7
PORT 2 DRIVERS
PORT 2
QUICK
LATCH
FLASH
STACK
PIONTER
AND TIMER BLOCKS
LATCH
PORT 3 DRIVERS
P3.0 ------ P3.7
PROGRAM
ADDRESS
REGISTER
BUFFER
PC
INCREMENTER
PROGRAM
COUNTER
DUAL DPTR