
3
AT89C51RB2/RC2
4180E–8051–10/06
Block Diagram
Figure 1. Block Diagram
Notes:
1. Alternate function of Port 1.
2. Alternate function of Port 3.
Timer 0
INT
RAM
256x8
T0
T1
Rx
D
Tx
D
WR
RD
EA
PSEN
ALE/
XTAL2
XTAL1
EUART
CPU
Timer 1
INT
1
Ctrl
INT
0
(2)
C51
CORE
(2) (2)
Port 0
P0
Port 1 Port 2 Port 3
Parallel I/O Ports & Ext. Bus
P1
P2
P3
XRAM
1Kx8
IB-bus
PCA
R
E
SET
PROG
Watch
Dog
PC
A
EC
I
Vs
s
V
CC
(2)
(1)
Timer2
T2
E
X
T2
(1)
Flash
32Kx8 or
16Kx8
Key
Board
ROM
2Kx8
Boot
+
BRG
SPI
MI
S
O
MO
S
I
SC
K
(1) (1) (1)
SS
(1)