27.6 PRACTICE PROBLEMS

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(Note: Problem solutions are available at http://sites.google.com/site/automatedmanufacturingsystems/)

1. Describe what the bits would be when an A (ASCII 65) is transmitted in an RS-232 interface with 8 data bits, even parity and 1 stop bit.

2. Divide the string in 'str_a' by the string in 'str_b' and store the results in 'str_c'. Check for a divide by zero error.

3. How long would it take to transmit an ASCII file over a serial line with 8 data bits, no parity, 1 stop bit? What if the data were 7 bits long?

4. Write a number guessing program that will allow a user to enter a number on a terminal that transmits it to a PLC where it is compared to a value in target. If the guess is above "Hi" will be returned. If below "Lo" will be returned. When it matches "ON" will be returned.

5. Write a structured text program that reads inputs from `channel 0'. An input string of `CLEAR' will clear a storage array. Up to 100 real values with the format `XXX.XX' will arrive on `channel 0' and are to be stored in the array. If the string `AVG' is received, the average of the array contents will be calculated and written out `Channel 0'.