MC81F4432
29.4 Entering ISP mode at power on time
Basically anytime +9v signal is forced to RESET/Vpp pin, the MCU is entering into ISP mode. But it
makes trouble when the RESET/Vpp pin is output mode. Because the +9v signal is clashing with the
port‟s output voltage.
But it is possible to enter the ISP mode at the power on time even RESET/Vpp pin is used as an
output mode. There is an oscillator stabilizing time when power is turn on. While in the time
RESET/Vpp pin is in input mode even it is used as an output mode in operation time.
A proper procedure is required to make sure that ISP board catch the oscillator stabilizing time to
enter the ISP mode. See following procedure.
1. Power off the target system.
2. Configure the target system as ISP mode.
3. Attach a ISP B/D into the target system.
4. Run the ISP S/W
5. Select the target device.
6. Power on the target system.
7. Execute ISP commands as you want.
Note :
Power on the target system after select the target device is essential. Because when target
device is selected, ISP board is getting ready to catch the proper timing to rise the Vpp(+9v)
signal.
October 19, 2009 Ver.1.35
185
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