
2
4428E–8051–02/08
AT/TS80C31X2
2.
Block Diagram
Timer 0
INT
RAM
128x8
T
0
T
1
R
x
D
T
x
D
WR
RD
EA
PSEN
ALE/
XTAL2
XTAL1
EUART
CPU
Timer 1
IN
T
1
Ctrl
IN
T
0
(1)
C51
CORE
(1) (1)
Port 0
P
0
Port 1 Port 2 Port 3
Parallel I/O Ports & Ext. Bus
P
1
P
2
P
3
IB-bus
R
E
S
E
T
PROG
(1)
(1): Alternate function of Port 3