8051 ISP by COM Port
1 Introduction
ISP
is the acronym of
I
n-
S
ystem
P
rogramming, which makes it possible that the user can update the program
memory under the software control without removing the mounted MCU chip from the actual end product. For the
8051 MCU products, we provide an ISP solution through the PC’s COM port. As long as the
Nuvoton standard ISP
code
is pre-programmed in the MCU’s LDROM, the user can easily update the MCU’s APROM through the PC’s
COM port.
Note:
The ISP function can work only when the ISP code has resided in MCU’s LDROM. To let users easily use the ISP function, some
of the 8051 MCU products have the “Nuvoton Standard ISP Code” pre-programmed in LDROM and CONFIG bits properly
configured before shipping. Please contact Nuvoton for detailed product information. (The “Nuvoton Standard ISP Code” is also
included in the folder [(3) Nuvoton Standard ISP Code]. The user may program it by himself using a universal programmer.
)
2 Hardware
To make the 8051 MCU boot from LDROM after reset to run the ISP code, some specific I/O pins need to be tied to
ground and the CONFIG needs to be properly configured. The following table shows the specific I/O pins and the
proper CONFIG setting used for booting from LDROM after reset. In addition, to directly connect to PC’s COM port,
there needs an RS232 transceiver (e.g. MAX232) in the target system. The following sub-sections will show the
hardware connection.
I/O Pins and CONFIG Bit for Booting from LDROM after Reset
Part No.
I/O Pins Tied to Ground for
Booting from LDROM
CONFIG Setting for
Booting from LDROM
W78E(I)051D
W78E(I)052D
W78E(I)054D
(Not Need)
“CBS”
Selected as LDROM
(Boot from LDROM)
P2.6 & P2.7 (for 40-pin package)
(Not Need)
W78E(I)058D
W78E(I)516D
W78E(L)365A
W78E065A
W78E858A
P4.3 (for 44-pin package)
(Not Need)
P2.6 & P2.7 (for 40-pin package)
“Reboot P2.6/P2.7”
Enabled
W78E(I)RD2A
W77E(L)516A
W77E(L)532A
W79E(L)632A
W79E(L)633A
W79E(L)648A
W79E(L)649A
W79E(L)658A
W79E(L)659A
P4.3 (for 44/68/100-pin package)
“Reboot P4.3”
Enabled
P3.6 & P3.7 (for 44-pin package)
“Reboot P3.6/P3.7”
Enabled
W79E217A
W79E225A
W79E226A
W79E227A
P4.3 (for 48/100-pin package)
“Reboot P4.3”
Enabled
W79E201A P4.0
“Reboot P4.0”
Enabled
W925EP01 P4.7
“Reboot P4.7”
Enabled
N78E366A
N78E055A
N78E059A
N78E517A
(Not Need)
“CBS”
Selected as LDROM
(Boot from LDROM)
©2010 Nuvoton Technology Corporation. All Rights Reserved.
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