Texas Instruments TI-83-Plus User Manual

124 Chapter 3: Application Development Process
TI-83 Plus Developer Guide Third Release May 28, 2002
Defining a String
Many system routines operate on null-terminated strings, which are a series of
characters followed by the byte 00h. The assembler supports null-terminated string
creation through use of the directive .asciz. This permits you to type the string in
readable text instead of defining each byte separately. Each character of the string is
translated to its ASCII code and stored at the current location and a null character is
then appended. In our example, we define a label that points to the first character of the
string so that we can point to the string in our system calls.
Erasing the Screen
To erase the screen, the example does the system call.
B_CALL ClrLCDFull ; Clear the screen
Printing Text to the Screen
To print text to the screen, the example uses the system call.
B_CALL PutS ; Print the hello string from RAM
This routine prints a null-terminated string in large text to the screen. It expects you to
have already set up the screen row and column where it should start printing the string.
The screen rows range from 0 (Top) to 7 (Bottom), and the columns range from 0 (Left)
to 15 (Right). You set these values in the system variable curRow and curCol prior to the
call. The PutS routine expects Z80 register HL to contain the address of the first
character of the string. It requires that this string be in RAM.
Copying the String
To copy a string from Flash ROM, where it is defined in your program, into RAM, where
the system routine PutS can use it, you can use the system routine StrCopy. This
routine expects the address of the source string to be in HL and the address of the first
RAM destination character to be in DE. It expects a null-terminated string. The example
copies the string Hello into the OP1 area in RAM (see next paragraph).
System RAM Registers
The calculator system code performs many operations on floating-point values. It uses a
floating-point format that requires up to 11 bytes in certain situations. Since floating-
point operations are so common, it defines six 11-byte areas that it uses frequently for
storing such numbers. It gives these RAM areas the name OP1, OP2, OP3, OP4, OP5,
and OP6. In our example, the system routines StrCopy and PutS do not use or modify
these areas, so we use six of the eleven OP1 RAM bytes to temporarily store our string
in RAM. In this case, we are just using OP1, since changing those locations is harmless;
the fact that OP1 may be used at some later time to pass floating-point data does not
matter.

Texas Instruments TI-83-Plus Specifications

General

Display Type	LCD
Display Resolution	96 x 64 pixels
Power Source	4 AAA batteries
Programming Language	TI-BASIC, Z80 Assembly
Backup Power	CR1616 or CR1620 lithium battery
RAM	24 KB
Processor	Zilog Z80
Weight	7.4 oz (210 g) with batteries
Dimensions	7.3 x 3.5 x 0.9 inches

Summary

Introduction

Conventions Used in this Guide

Defines conventions for program text, syntax, and optional parameters in guide examples.

Purpose of this Guide

Explains the types of programs that can be created and the guide's focus on Flash ROM apps and RAM assembly programs.

TI-83 Plus Specific Information

ARCHITECTURE

Describes the TI-83 Plus architecture composed of several layers: Hardware, Drivers, Tools, and Programming.

HARDWARE LAYER

Covers the Zilog Z80 CPU, RAM, and Flash ROM components of the TI-83 Plus unit.

Z80 RAM Structure

Explains the 32K RAM partitioning into areas like System RAM, User RAM, and Floating Point Stack.

Flash ROM Structure

Details the 512K Flash ROM composition, divided into 32 pages of 16K each.

System Routines

Explains accessing TI-83 Plus system routines using Z80 RST instruction and macro-instructions.

Variable Naming Conventions

Outlines rules for naming variables, including predefined and user-defined names and their formats.

System Variables Area

Describes preallocated system RAM variables essential for built-in functionality.

DRIVERS LAYER

Covers keyboard input, display access, and link port communication functionalities.

Display

Details accessing the TI-83 Plus display via system routines or directly writing to the display driver.

Graphing and Drawing — What’s the difference?

Differentiates between pixel-based drawing routines and graph routines tied to WINDOW settings.

TOOLS AND UTILITIES LAYER

Covers essential development tools like error handlers, utility routines, and debugging features.

Error Handlers

Explains setting up error exception handlers using AppOnErr and AppOffErr macros to capture system errors.

Temporary Variables

Discusses temporary variables used for intermediate results and their management.

Entering and Exiting an Application Properly

Details how applications interact with the TI-83 Plus application loader and state monitor.

Application Development Process

PROGRAMMING LAYER

Covers the final layer of TI-83 Plus architecture, focusing on TI BASIC, ASM, and Applications.

Applications

Defines applications as Flash ROM programs, their PC creation, signing requirements, and larger scale.

DEVELOPMENT SYSTEM

Introduces the simulator for general development, setup, and sample application creation.

Using the Simulator System — Requirements for Getting Started

Lists requirements for TI-83 Plus application development using Zilog Developer Studio and TI Simulator/Debugger.

Debugging the Application

Demonstrates setting breakpoints, modifying RAM, and using the Memory Map view for debugging.

Downloading the Application

Explains using TI GRAPH LINK or TI Connect to download applications to calculators.

Development Tools

DEVELOPMENT ARCHITECTURE

Outlines the TI development architecture based on the TI simulator/debugger and Zilog Developer Studio.

TI SOFTWARE SIMULATOR AND DEBUGGER

Describes the TI-83 Plus simulator for debugging applications, detailing menu options and operations.

Breakpoints

Explains setting and removing breakpoints via the manual setup dialog box in the debugger.

CPU View Window

Displays processor information such as index registers, stack pointer, and flags.

Flash View Window

Displays entire Flash memory contents, allowing address viewing and toggling between physical/logical modes.

RAM View Window

Displays entire RAM contents, allowing address viewing and toggling between physical/logical modes.

Key Press Recording and Playback

Allows recording and playing back key presses, with setup options for files and rates.

Support in Writing Applications

Lists resources for help in writing TI-83 Plus applications, including guides and tutorials.

Glossary

TI-83 Plus “Large” Character Fonts

TI83 Plus “Small” Character Fonts