Purpose: The general purpose of this laboratory is to familiarize you with the software development steps using the Keil uVision simulator. In the following labs, we will use uVision for both simulation and debugging on the real board, but for this lab, we will just use the simulator. You will learn how to perform digital input/output on parallel ports of the TM4C123. Software skills you will learn include port initialization, logic operations, and unconditional branching.
Do not use any conditional branches in your solution! We want you to think of the solution in terms of logical and shift operations. Logical operations include AND, ORR and EOR. Shift operations include LSL and LSR.
System Requirements:
The objective of this system is to implement an an even parity system. There are three bits of inputs and one bit of output. The output is in positive logic: outputing a 1 will turn on the LED, outputing a 0 will turn off the LED. Inputs are negative logic: meaning if the switch not pressed is the input is 1, if the switch is pressed the input is 0.
PEO is an input
PE1 is an input
PE2 is an input
PE3 is the output
The specific operation of this system
• Initialize Port E to make PEO, PE1, PE2 inputs and PE3 an output
• Make the output 1 if there is an odd number of switches pressed, otherwise make output o.
• Over and over, read the inputs, calculate the parity bit and set the parity bit at the output
The input data refers to the switch, not the input. The following table illustrates the expected behavior relative to output PE3 as a function of inputs PEO, PE1, PE2 (negative logic with respect to the switches). PE2 0 0 0 0 PE1 0 0 1 1 0 0 PEO 0 1 0 1 0 1 0 1 РЕЗ 1 0 0 1 0 1 1 0 number of O's in 3 input bits odd even even odd even odd odd even 1 1 1 1 1 1
There are 8 valid output values for Port E: 0x01,0x02,0x04,0x07,0x08,0x0B,0xOD, and OxOE. General rule, PEO, PE1, PE2, PE3 always have an odd number of O's.
You could also consider the specification the LED output as a function of the switch input. The following table illustrates the expected behavior relative to LED output as a function of switch presses Sw2 Sw1 Swo press press press press press not press not press press not not not press press not press not not not press not not not LED On Off Off On Off On On Off number switches pressed odd even even odd even odd odd even
where press means the switch is pressed and not means the switch is not pressed.