Two 16F873A microcontrollers are to be connected together with a synchronous serial link, operating in SPI (Serial Peripheral Interface) mode. One is to act as Master, the other as Slave. No other nodes are required. Data needs to be sent in both directions. A serial bit rate of 2MHz is required. Each microcontroller is running with an 8 MHz crystal oscillator. Draw a simple block diagram, showing the two microcontrollers and indicating how the serial connection is made. Clearly label the pins being used. Show on your diagram which is Master and which Slave. You need show only the connections necessary for the serial link; no other connections need be shown. For each microcontroller, indicate how SSPCON1 should be configured. Consider only bits 0 to 5, and use X to show \'don\'t care\' for bits which have no impact on this particular requirement. Briefly explain each selection made. Explain briefly the disadvantages of a simple serial protocol like this, for example in situations where multiple nodes and high reliability are required.
if you want connect two two microcontrollers and indicating how series connectionproblem is as you have mentioned, programming errors. There is a potential for issues, so you have to code carefully. Other than that, as long as the pins are not both outputs with different levels, it is fine.Using two pins to drive an led (or two) is also not uncommon. While not using a resistor is not recommended, you can get away with it. If your output voltage is relatively close to the led forward voltage, then current draw may not be an issue. And there is the pin voltage droop. As current sourced Increases, Voltage at that pin Decreases (Vcc to Vcc - 0.3 to -1, etc). As current sinked Increases, the Voltage Increases (From Gnd to Gnd + 0.3v to + 1v, etc). It is a bit of a self correcting blessing, but shouldn\'t be relied upon.
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