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下面是DS87C550 简介:
    The DS87C550 EPROM High-Speed Microcontroller with ADC and PWM is a member of the fastest 100% 8051-compatible microcontroller family available. It features a redesigned processor core that removes wasted clock and memory cycles. As a result, it executes 8051 instructions up to three times faster than the original architecture for the same crystal speed. The DS87C550 also offers a maximum crystal speed of 33MHz, resulting in apparent execution speeds of up to 99MHz.
  The DS87C550 uses an industry standard 8051 pin-out and includes standard resources such as three timer/counters, and 256 bytes of scratchpad RAM. This device also features 8kB of EPROM with an extra 1kB of data RAM (in addition to the 256 bytes of scratchpad RAM), and 55 I/O ports pins. Both One-Time-Programmable (OTP) and windowed packages are available. Besides greater speed, the DS87C550 includes a second full hardware serial port, seven additional interrupts, a programmable watchdog timer, brownout monitor, and power-fail reset.
  The DS87C550 also provides dual data pointers (DPTRs) to speed block data memory moves. The user can also dynamically adjust the speed of external accesses between two and 12 machine cycles for flexibility in selecting memory and peripherals.Power Management Mode (PMM) is useful for portable or battery-powered applications. This feature allows software to select a lower speed clock as the main time base. While normal operation has a machine cycle rate of 4 clocks per cycle, the PMM allows the processor to run at 1024 clocks per cycle.For example, at 12MHz, standard operation has a machine cycle rate of 3MHz. In Power Management Mode, software can select an 11.7 kHz (12MHz/1024) machine cycle rate. There is a corresponding reduction in power consumption due to the processor running slower.
  The DS87C550 also offers two features that can significantly reduce electromagnetic interference (EMI). One EMI reduction feature allows software to select a reduced emission mode that disables the ALE signal when it is unneeded. The other EMI reduction feature controls the current to the address and data pins interfacing to external devices producing a controlled transition of these signals.
  87C52 Compatible
  - 8051 pin and instruction set compatible
  - Three 16-bit timer/counters
  - 256 bytes scratchpad RAM
  On-Chip Memory
  - 8kB EPROM (OTP & Windowed Packages)
  - 1kB extra on-chip SRAM for MOVX access
  On-Chip Analog-to-Digital Converter
  - Eight channels of analog input, 10-bit resolution
  - Fast conversion time
  Pulse-Width Modulator Outputs
  - Four channels of 8-bit PWM
  - Channels cascadable to 16-bit PWM
  Four Capture plus Three Compare Registers
  55 I/O Port Pins
  New Dual Data Pointer Operation
  - Either data pointer can be incremented or decremented
  ROMSIZE Feature
  - Sets effective on-chip ROM size from 0 - 8kB
  - Allows access to entire external memory map
  - Dynamically adjustable by software
  High-Speed Architecture
  - 4 clocks/machine cycle (8051 = 12)
  - Runs DC to 33MHz clock rates
  - Single-cycle instruction in 121ns
  - New Stretch Cycle feature allows access to fast/slow memory or peripherals
  Unique Power Savings Modes
  EMI Reduction Mode Disables ALE if Not Needed
  High-Integration Controller Includes:
  - Power-fail reset
  - Early-warning power-fail interrupt
  - Two full-duplex hardware serial ports
  - Programmable watchdog timer
  16 Total Interrupt Sources with Six External
  Available in 68-Pin PLCC, 80-Pin PQFP, and 68-Pin Windowed CLCC