8051 microcontrollers

Development Systems for Microcontrollers What is needed to be able to apply a microcontroller to your product? That is, what package of hardware and software will allow the microcontroller to be programmed and connected to your application? A package commonly called a development system is required. First, trained personnel must be available either on your technical staff or as consultants. One person who is versed in digital hardware and compute^ software is the minimum number. Second, a device capable of programming EPROMs must be available to -test the prototype device. Many of the microcontroller families discussed have a ROMless version, an EPROM version, or an electrically erasable and program­mable read only memory (EEPROM) version that lets the designer debug the hardware and software prototype before committing to full-scale production; Many inexpensive EPROM programmers are sold that plug into a slot of most" popular personal computers. More expensive, and more ...

A Microcontroller Survey Markets for microcontrollers can run into millions of units per applica­tion. At these volumes the microcontroller is a commodity item and must be optimized so that cost is at a minimum. Semiconductor manufacturers have produced a mind-numbing array of designs that would seem to meet almost any need. Some of the chips listed in this section are no longer in regular pro­duction, most are current, and a few are best termed "smokeware": the dreams of an aggressive marketing department. Four-Bit Microcontrollers In a commodity chip, expense is represented more by the volume of the package and the number of pins it has than the amount of silicon inside. To minimize pin count and package size, it is necessary that the basic data word-bit count be held to a minimum, while still enabling useful intelligence to be implemented. Although 4 bits, in this era of 64-bit "maximicros," may seem somewhat ludicrous, we must recall that the original ...

Questions Find the following using the information provided in Chapter 2. 1. Size of the internal RAM. 2. Internal ROM size in the 8031. 3. Execution time of a single byte instruction for a 6 megahertz crystal. 4. The 16-bit data addressing registers and their functions. 5. Registers that can do division. 6. The flags that are stored in the PSW. 7. Which register holds the serial data interrupt bits TI and RI. 8. Address of the stack when the 8051 is reset. 9. Number of register banks and their addresses. 10. Ports used for external memory access. 11. The bits that determine timer modes and the register that holds these bits. 12. Address of a subroutine that handles a timer 1 interrupt. 13. Why a low-address byte latch for external memory is needed. 14. How an 1/0 pin can be both an input and output. 15. Which port has no alternate functions. 16. The maximum pulse rate that can be counted on pin T1 if the oscillator frequency is 6 megahertz. 17. Whic...

Summary The internal hardware configuration of the 8051 registers and control circuits have been examined at the functional block diagram level. The 8051 may be considered to be a col­lection of RAM, ROM, and addressable registers that have some unique functions. SPECIAL-FUNCTION REGISTERS Register Bit Primary Function Bit Addressable A 8 Math, data manipulation Y B 8 Math Y PC 16 Addressing program bytes N DPTR ...

Interrupts A computer program has only two ways to determine the conditions that exist in internal and external circuits. One method uses software instructions that jump on the states of flags and port pins. The second responds to hardware signals. called interrupts. that force the program to call a sub-routine. Software techniques use up processor time that could be devoted to other tasks; interrupts take processor time only when action by the program is needed. Most applications of microcontrollers involve responding to events quickly enough to control the environment that generates the events (generically termed "real- FIGURE 17 IE and IP Function Registers THE INTERRUPT ENABLE (IE) SPECIAL FUNCTION REGISTER Bit symbol Function 7 EA Enable interrupts bit. Cleared to 0 by progra...

Serial Data Input/Output Computers must be able to communicate with other computers in modern multiprocessor distributed systems. One cost-effective way to communicate is to send and receive data bits serially. The 8051 has a serial data communication circuit that uses register SBUF to hold data. Register SCON controls data communication, register PCON controls data rates, and pins RXD (P3.0) and TXD (P3.1) connect to the serial data network. SBUf is physically two registers. One is write only and is used to hold data to be transmitted out of the 8051 via TXD. The other is read only and holds received data from external sources via RXD. Both mutually exclusive registers use address 99h. There are four programmable modes for serial data communication that are chosen by setting the SMX bits in SCON. Baud rates are determined by the mode chosen. Figure 13 shows the bit assignments for SCON and PCON. Serial Data Interrupts Serial data communication is a relatively slow process, o...

Counters and Timers Many microcontroller applications require the counting of external events, such as the frequency of a pulse train, or the generation of precise internal time delays between com­puter actions. Both of these tasks can be accomplished using software techniques, but software loops for counting or timing keep the processor occupied so that other, perhaps more important, functions are not done. To relieve the processor of this burden, two 16-bit up counters, named T0 and T1, are provided for the general use of the programmer. Each counter may be programmed to count internal clock pulses, acting as a timer, or pro­grammed to count external pulses as a counter. Bit Symbol Function 0 IT0 External interrupt 0 signal type control bit. Set to 1 by program to enable external interrupt...