Intel mcs-48 Developing An MCS-48 Based Product, Education, Function Definition, Code Generation

INTRODUCTION

1.3Developing An MCS-48™ Based Product

Although the development of a microcom- puter based product may differ in detail from the development cycle of a product based on TTL logic or relays, the basic procedures are the same - only the tools are different.

1.3.1 Education

The first step of course is to become familiar with what the microcomputer is and what it can do. The first step in this education is this document, the MCS-48™ User'sManual. The user'smanual gives a detailed description of the MCS-48 family of components and how they may be used in various system configu- rations. Also included is a description of the 8048 instruction set and examples of how the instructions may be used. For a more complete discussion of the instruction set and programming techniques the MCS-48 Assembly Language Manual is also available.

If time is critical in getting started in microcomputers, individuals can attend one of many Intel sponsored 5-day training courses which give basic instruction in the MCS-48 as well as hands-on experience with MCS-48 development systems. These courses are a convenient means of getting started with the MCS-48, particularly for those not familiar with microprocessors.

After general familiarization is complete, either through self-instruction or a training course, the next step is to gain a better "feel" for what a microprocessor can do in your own applications by writing several exercise programs which perform basic functions. You may require such things as I/O routines, delays, counting functions, look-up tables, arithmetic functions, and logical operations which can serve as a set of building blocks for future applications programs. Several basic programming examples are included in the MCS-48 Assembly Language Manual while the Intel User'sLibrary is a source of more specific applications routines.

1.3.2 Function Definition

After a thorough understanding of the

microprocessor is achieved, the functions to be implemented can be defined using a flowchart method to describe each basic system function and the sequence in which the processor executes these functions. Once the system is flowcharted, critical time- related functions can be identified and sample programs written to verify that performance requirements can be met.

1.3.3 Hardware Configuration

The next step involves the definition of the microcomputer hardware required to imple- ment the function. Input/Output capability must be defined in terms of number of inputs, number of outputs, bi-directional lines, latching or non-latching I/O, output drive capability, and input impedance. The num- ber of words of RAM storage required for intermediate results and data storage must then be determined. The type of system will dictate whether battery backup is needed to maintain data RAM during power failure.

Probably the most difficult parameter to define initially is the amount of program memory needed to store the applications program. Although previously written exer- cise programs will make this estimate more accurate, a generous amount of "breathing room" should be allowed in program memory until coding is complete and the exact requirements are known. Many special functions such as serial communications (TTY) or keyboard/display interfaces may be implemented in software (programs); how- ever, in cases where these functions place a severe load on the processor in terms of time or program memory, special peripheral interface circuits such as the 8251, Universal Synchronous or Asychronous Receiver/ Transmitter (USART) or 8279 Keyboard/ Display interface may be used.

1.3.4 Code Generation

The writing of the final program code for the application can begin once the system function and hardware have been defined and can be generated in parallel with the detailed hardware design (PC card layout, power supply, etc.)

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