Test Execute and Simulate

Jonathan Valvano, September 6, 2006


Lesson 1. Introduction (11 minutes)

            Lesson 1 provides a brief introduction to TExaS. In this lesson, I will show you the minimal components required to design a simple assembly program.  In particular, I will edit, assemble and simulate a 6812 program. This program will execute a loop 10 times then stop.

; lesson 1

      org  $3800

count rmb  1

      org  $4000

main  ldaa #10    ;loop counter

      staa count

loop  dec  count  ;9,8,...,0

      bne  loop


      org  $FFFE

      fdb  main


Lesson 2. Run modes and the ViewBox (11 minutes)

            This lesson explains some of the debugging features available with TExaS. A vast amount of information exists as the computer executes software. A good debugger allows us to selectively filter this information, showing us only data relevant to problem at hand. There are two aspects of this filter: what information will we see? and when (or how often) will it be collected? The run mode allows us to adjust the level of detail observable during the simulation.


Lesson 3. Input/output using switches and LEDs (13 minutes)

            Lesson 3 introduces the I/O window. The embedded system that we will implement create a simple NOT gate with the input on port pin PT1 and the output on port pin PT0. In particular, we will edit, assemble and simulate a 6812 program, which inputs from a switch complements the value and outputs it to an LED.

;lesson 3

PTT   equ  $0240

DDRT  equ  $0242

      org  $4000

main  ldaa #$01   ;PT1 input, PT0 output

      staa DDRT

loop  ldaa PTT    ;read switch

      eora #$02   ;complement

      lsra        ;bring value into bit0 position

      staa PTT    ;set LED

      bra  loop

      org  $FFFE

      fdb  main


Lesson 4. TExaS help system (under construction)

   Lesson 4 illustrates some of the help features available in TExaS. There are two types of problems that are addressed by the TExaS help system. First, we will consider questions about TExaS itself. Second, I will show you how to use the help system while writing your assembly code.