LAB 2: Hardware Interfacing – Keypad CEG 3136 - Computer Architecture II Fall 2018 School of Enginee

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LAB 2: Hardware Interfacing – Keypad CEG 3136 - Computer Architecture II Fall 2018 School of Engineering and Computer Science University of Ottawa

Experiment Date: 01/10/2018 Submission Date: 15/10/2018 OBJECTIVES ● To familiarize ourselves with the Motorola 9S12DG256. ● To implement a basic keypad unit.

MATERIALS AND COMPONENTS ● Windows PC ● MiniIDE software ● Dragon-12 board and associated cables INTRODUCTION The purpose of this lab is to implement a connection between the keypad of a Dragon-12 board and an arming/disarming system. This employs concepts we familiarize ourselves with during the previous lab.

DESIGN Part 1 To implement KeyPad.asm, we have to consider what it does. It must take in which key on the Dragon-12 keypad as input and manipulate its corresponding ASCII value.

The subroutine pollReadKey checks for key presses on the Dragon-12 and converts to ASCII if so.

The subroutine readKey takes the associated value of keys pressed on the Dragon-12, but it also accounts for faulty presses and brief taps with a delay beforehand.

The readKeyCode subroutine involves three nested conditional statements for the four rows on the keypad. The logic behind this employs the understanding that each row on the keypad should detect key presses for a moment, and if one is pressed, indicate which key. Finally, the subroutine returns the changed PORTA value.

The simplest yet most time-consuming subroutine is translate, which takes the value from the previous subroutine and translates it to the corresponding and necessary ASCII code. This is achieved with many conditional statements.

PART 2 We are tasked with implementing the subroutine delayms, relevant to the one employed above, which consists two loops in a nested structure. The inner loop creates a 1-millisecond delay while the outer loop multiplies this delay as required. The concepts employed here are from the delay module in lab 1.

TESTING As corroborated by our lab instructor, our pre-lab designs, give-or-take several syntactic corrections, were successful. Attached are the KeyPad.asm and updated delay.asm that were developed and analyzed.

CONCLUSION In this lab, we employed prior knowledge and some new readings to implement a connection between a physical keypad and software subroutines. This lab considers the concept of time and sequence in a more comprehensive manner than before. The assembly code produced in this lab may be employed in future projects with more complex functionalities.