Texas Instruments TI-83-Plus User Manual

Chapter 2: TI-83 Plus Specific Information 19
TI-83 Plus Developer Guide Third Release May 28, 2002
statVars
(8A3Ah)
This is the start of 531 bytes of RAM used to store statistical
results. If you use this area, do not compute statistics in your
ASM program. Make this B_CALL to invalidate statistics, as well.
B_CALL DelRes
appBackUpScreen
(9872h)
This is the start of 768 bytes of RAM not used by the system. It is
intended for ASM and applications. Its size is large enough to
hold a bit image of the display, but it can be used for whatever
you want.
tempSwapArea
(82A5h)
This is the start of 323 bytes used only during Flash ROM
loading. If this area is used, avoid archiving variables.
WARNING: The RAM is safe to use only until the application exits. Data in any of these areas of RAM may
be destroyed between successive executions of an application. Therefore, any data that must
remain between executions cannot be kept in these areas. This RAM is only for the variables
that can be discarded when the application exits.
System Variables Area
This area of system RAM consists of preallocated variables needed by much of the TI-
83 Plus built-in functionality. Because they are floating-point numbers these variables
are all nine bytes. Because these variables are always needed, the system always
keeps them around and never changes their addresses.
There are two classes of system variables — those that you can store to and recall
from, and those that are referred to as output only variables because the system
routines can store to them.
System Variables that are Both Input and Output
In general, these values should only be changed by system routines that applications
can call. Modifying these variables directly, rather than modifying them through the
appropriate system routine, could corrupt the state of the system. Most of these system
variables have restrictions on what values are valid to store to them. Using the system
routine to store to them guarantees that the proper checks are made on the values
being stored to them.
System Variable Characteristics
• There are no Symbol Table entries for system variables.
• These variables can be changed by the user, but cannot be deleted or renamed. For
example, you can change Xmax, but you cannot delete it.
• These variables are initialized to a predetermined value upon reset.
• These variables always reside in RAM. For example, it is not possible to archive
Xmin.

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