Hello all,

I am working on a new design. It is in schematic stage as of now.

For these microcontrollers, the MISO, MOSI, SCK and RESET lines are used for ISP of the Flash Program memory.

In my circuit, ADC MCP3201 (a SPI device) is connected to MISO and SCK lines. MOSI is left unconnected. For RESET, I have used a MAX708.

Now to perform the ISP operation, the ISP lines should not be disturbed by other circuits. So what I have done is provided a manual switch to switch off the supply to MCP3201. RESET pin is directly connected to the ISP header.

I just want to confirm whether this will work correctly?
Another alternative is to use an electronic switch between the ADC pins and the microcontroller pins. Enable the switch in normal mode and disable it in program mode.

Which of the above two alternatives is better? Or any other alternative?

Schematic:


AT89S51 datasheet:
http://www.atmel.com/dyn/resources/prod_documents/doc2487.pdf

MCP3201 datasheet:
http://ww1.microchip.com/downloads/en/DeviceDoc/21290D.pdf


Regards,