From Microcontrollers in Practice

11.1 In this Chapter

This chapter contains the description of a simple development board for the study of the 8051 family of microcontrollers ? Unlike the development boards dedicated to the HC11 and AVR families, presented in the previous chapters, this project allows the user to load and execute programs in an external RAM area, addressed to be visible both in the program memory and data memory address space.

11.2 Hardware

The schematic of the board is presented in Fig .11.1, 11.2, and 11.3. Figure 11.1 shows the microcontroller IC10, the bus demultiplexer IC7, the RS232 interface IC12, the RESET and clock circuits, and the ISP connector SV1.


Figure 11.1: MCU, bus demultiplexer, RESET, clock, and RS232

Note the presence of the two NAND gates IC6C and IC6D, which implement the logic function AND between the signals RD\ (Read) and PSEN\ (Program Store Enable), both active LOW, and generate the signal RDPSEN. RDPSEN is active LOW when either RD\ or PSEN\ is LOW. Connecting this signal to the RD\ input of an external RAM circuit allows the use of this RAM to store program as well as data.

The microcontroller can be any of 8032, 8051, 8052, AT89C51, AT89C52, etc. in a DIP40 package. The input EA\ (External Access) of the MCU is connected to the jumper JP1 to allow the use of the internal ROM, if this is available. Connect the jumper so that EA\ = 1 to use the internal ROM. When the external ROM is...


Products & Services
Microcontrollers (MCU)
Microcontrollers (MCUs) are complete computer systems on a chip. They combine an arithmetic logic unit (ALU), memory, timer/counters, serial port, input/output (I/O) ports and a clock oscillator.
Memory Chips
Memory chips are internal storage areas in computers. Although the term "memory chip" commonly refers to a computer's random access memory (RAM), this product area includes many different types of electronic data storage. Computer memory stores data electronically in cells. Without memory chips, a computer could not read programs or retain data.
CompactPCI Controllers and CompactPCI Processors
CompactPCI controllers and CompactPCI processors are rugged, high-speed computer boards and single board computers that control data transfers between devices in CompactPCI and PXI networks. These devices also control the status of interrupts, interrupt requests (IRQs), registers, and triggers as well as network instruments for testing and analysis.
Human Machine Interfaces
Human machine interfaces (HMI) are operator interface terminals with which users interact in order to control other devices.
Single Board Computers (SBC)
Single board computers (SBC) serve as the motherboard for instrumentation systems including modern PCs. SBCs are composed of a microprocessor, memory chip, and serial and parallel interfaces to communicate with other devices.

Topics of Interest

12.1 In this Chapter This chapter contains a didactic example on how to use the AVR development board described in Chap. 10 as an 8-channel digital voltmeter that can be interrogated over the RS232...

Before one uses the microcontroller, he or she should be well aware of the connections of the microcontroller, like which pins are to be used as data pins and which pin is to be given the power...

A.4 An Example of Expanded Structure with HC11 The example presented below is an illustration of a typical structure with 68HC11E9 operating in expanded multiplexed mode (MODA = 1, MODB = 1). Figure...

3.7 USING THE MICROCONTROLLER Before one uses the microcontroller, he or she should be well aware of the connections of the microcontroller, like which pins are to be used as data pins and which pin...

A.8 AT90S8515 Operating with External RAM Some AVR microcontrollers can allocate some of the I/O lines to extend the bus of the data memory for connecting external memory or other RAM-like external...