
3
4188F–8051–01/08
AT/TS8xC51Rx2
3.
Block Diagram
Timer 0
INT
RAM
256x8
T
0
T
1
R
x
D
T
x
D
WR
RD
EA/VPP
PSEN
ALE/
XTAL2
XTAL1
EUART
CPU
Timer 1
IN
T
1
Ctrl
IN
T
0
(3)
C51
CORE
(3) (3)
Port 0
P
0
Port 1 Port 2 Port 3
Parallel I/O Ports & Ext. Bus
P
1
P
2
P
3
XRAM
256/768x8
IB-bus
PCA
R
E
S
E
T
PROG
Watch
Dog
P
C
A
E
C
I
V
s
V
c
(3)
(1)
(1): Alternate function of Port 1
(3): Alternate function of Port 3
(1)
Timer2
T
2
E
X
T
2
(1)
Port 5
Port 4
P
5
P
4
(2): Only available on high pin count packages
(2)
ROM
/EPROM
0/16/32/64Kx8