This application is a digital voltmeter reading the ADC and displaying the
result on the MDM-1, in addition a demo of the display capabilities is available.
Set RD0=0 for voltmeter and RD0=1 for display demo.

In this application the Vref+ is the supply voltage (+4.95V on my sample) and
Vref- is 0V. Scaling is 4.883mV per division but there will be some error
depending on the exact value of the supply.  In real life it is better to use
a reference of say 4.096V as the ADC has 10bit resolution (1024 steps) then each step
is of equal value and calibration is not dependant on the setting of the power supply.

I have used the inbuilt CCS routines (delay, adc & RS232) plus there 877 definitions.

Serial data from the voltmeter is transmitted at 19200,8,N,1.

The checksum of the code is 966D.

