FIGURE 9.22
• 8-BIT FIXED POINT
• HIGHLY IMPROVED VERSION OF THE ORIGINAL MEMBER 8751/8051 IN MCS-51 FAMILY
• 4K x 8 EPROM, 128 x 8 RAM, 16-MHz, 0.75-^is INSTRUCTION CYCLE TIME
• SIX 8-BIT MULTIFUNCTION BIDIRECTIONAL PARALLEL PORTS
• THREE 16-BIT PROGRAMMABLE DEDICATED TIMERS/COUNTERS (ONE
WITH UP/DOWN MODE)
• TWO 16-BIT PROGRAMMABLE COUNTER ARRAYS WITH:
COMPARE/CAPTURE, SOFTWARE TIMER, HIGH-SPEED OUTPUT, PWM MODULATOR, AND WATCHDOG TIMER FUNCTIONS
• 8-CHANNEL ANALOG-DIGITAL CONVERTER WITH 8-BIT RESOLUTION
AND COMPARE MODE
• FULL-DUPLEX PROGRAMMABLE SERIAL PORT WITH SERIAL EXPANSION PORT
• HARDWARE WATCHDOG TIMER
• IDLE AND POWER DOWN MODES
• MCS-51 FAMILY INSTRUCTION SET
• BOOLEAN PROCESSING, MULTIPLY, DIVIDE INSTRUCTIONS
Microcomputers/DSPs of various types are available from a number of manufacturers. In this topic, we briefly review a few sample types manufactured by Intel and Texas Instruments. This figure summarizes the main features of an Intel 87C51-8-bit fixed-point microcomputer [14], which is an enhanced version of the older MCS-51 family. The architecture of the device is shown in the next figure. Recently, Intel has added the MCS-251 family (8-bit) as further upgrading of the MCS-51 family. In addition, the 16-bit MCS 96/296 family is also part of the existing product lines. The 8-bit computer can be used for small projects and when high performance is not required. The computer can be operated at either 12 or 16 MHz. The on-chip EPROM and RAM capacity is indicated. For large programs and large amounts of data, external memory can be added. One special feature of the computer is that it has an 8-channel, 8-bit A/D converter that operates in the multiplexed mode or individual selection mode. The computer can process Boolean variables. It has three 16-bit counters and two additional 16-bit programmable counter arrays that can generate PWM signals for the converter along with additional timing functions. The six bidirectional parallel I/O ports can be programmed for external hardware interrupts, serial ports, timer clock input, read/write signals for external memory, etc. The watchdog timer invokes a reset signal (unless a periodic hold-off signal prevents this reset). The timer helps detect hardware and software malfunctions. There is a set of 8-bit special function registers (SFRs), some of which are bit and byte addressable. A common instruction set is applicable to all the members of the MCS-51 family.