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You are here: 8051 Tools PAULMON Monitor Manual Using Serial Port | Search PJRC |
Here is one simple circuit that accomplishes this using 7 NAND gates. The 74HC00, 74LS00, 7400, CD4011 or other similar chips should work for this application. Be sure to check the pinouts before wiring
A similar circuit can be constructed using a DPDT relay (don't forget a transistor to drive the coil), with pullup resistors on the various signal lines so that they will remain at a logic high when they are physically disconnected by the relay contacts.
This simple technique does require extra circuitry on the development board, and one extra port pin, which won't be used in the final application. However, it does allow the use of PAULMON to develop the code and once the downloaded program is running with the SELECT line low, the program need not know that PAULMON uses the other serial port.