LEDs

The LEDs on the MCBSTR730 board are:

• A 5V_OK LED shows the DC voltage 5V status. The LED is switched off if the voltage is below its nominal value, or if the reset button is pressed.
• A 2-digit 7-segment LED display

• P0.0 – P0.7 connect to the seven segments A to G and the decimal dot of both digits. Setting the port output to zero switches the appropriate LED segment on.
• P0.8 – P0.9 connect to two transistors that enable the left and the right digit individually. Setting the port output to zero enables the appropriate digit.
• Because of this wiring scheme, a time multiplex method must be used to statically display a 2-digit value on the display.
  
  First, the on/off information for the first digit must be output at port P0.0 – P0.7 together with the enable signal for that digit. This value should be kept stable for some micro seconds.
  
  Then, the on/off information for the second digit must be output together with the enable signal for the second digit. This should be kept stable for the same amount of time.