8051 ISP by COM Port
©2010 Nuvoton Technology Corporation. All Rights Reserved.
< Revision 5.02 > 5
2.1 With an RS232 Transceiver in the Target System
In this design, each target system has an RS232 transceiver (e.g. MAX232) inside, and so only one RS232 cable is
needed during the ISP operation, as shown below.
Note 2:
For "With Reset Control" configuration, Q1, R3 and R4 are needed.
For "Without Reset Control" configuration, Q1, R3 and R4 are not needed.
C3
10p
PC
C6
1u/16V
VCC
RXD
COM Port
VCC
U2
MAX232
1
3
4
5
11
10
12
9
2
6
14
7
13
8
15
16
C1+
C1-
C2+
C2-
T1_IN
T2_IN
R1_OUT
R2_OUT
V+
V-
T1_OUT
T2_OUT
R1_IN
R2_IN
GN
D
VC
C
RTS
Note 1:
The I/O pins used for booting from LDROM may be P2.6&P2.7, P4.3, P3.6&P3.7, P4.0 or none.
(See the above table.)
P2.7
RST
VCC
RST
R4
10K
RS232
Transceiver
RS232
Connector
P3.0(RXD)
U1
RXD
TXD
Target System
R2
10K
X1
Fosc
RD
TD
DCD
P2.6
P3.1(TXD)
R3
4.7K
C2
10p
UA RT
In te rfa ce
8051 MCU
GND
CTS
P1
Male DB9
5
9
4
8
3
7
2
6
1
RI
GND
To b o o t fro m L DRO M.
(S e e No te 1 )
C1
2u
R1
47K
TXD
C4
1u/16V
C5
1u/16V
/EA
XTAL1
VCC
VCC
RS232 Cable
Q1
2N3906
XTAL2
C7
1u/16V
Fo r re se t co n tro l .
(S e e No te 2 )
DSR
(with RS232 Transceiver)
DTR
