1 Introduction

At present, with the continuous improvement of the level of science and technology, industrial and agricultural production, and higher and higher requirements for the corresponding instruments and meters, the instrumentation needs to expand a large number of peripheral functional components to meet the complexity and high performance of instrumentation. Intelligent requirements, although this method satisfies the complexity requirements of the instrument, the problem that comes with it is that the system is too complex and the system reliability is reduced, the failure rate is increased, the fault is difficult to find, and the intelligence is lost. The advantages of instrumentation, if you can integrate all or most of the peripheral functions that are complex in function into the microcontroller used in the system, the reliability of the instrumentation system can be greatly improved, and the cost of the system can be reduced. The on-chip resources of the single chip can be used to enhance the performance of the instrument without increasing the hardware cost. Therefore, the solution is an effective method for improving the reliability and performance of the instrument, and the C8051F020 single chip of the American Cygnal company is one type. A microcontroller for complex high performance instrumentation.

The C8051F020 microcontroller is a mixed-signal system-level microcontroller integrated on a single chip. It has a microcontroller that is fully compatible with the MCS?51 core and instructions. In addition to the digital peripheral components of the standard 8051 machine, the analog components and other digital peripherals and functional components commonly used in data acquisition and control systems are integrated on-chip, including analog multiplexers, programmable gain amplifiers, and ADCs. , DAC, Voltage Comparator, Voltage Reference, Temperature Sensor, SMBus/I2C, UART, SPI, Programmable Counter/Timer Array, Timer, I/O Port, Power Monitor, Watchdog Timer, and Clock Oscillator Etc., and the microcontroller has JTAG and debug circuitry inside, through the JATG interface, the microcontroller installed on the final application system can be used for non-intrusive, full-speed and system debugging.

2 functions and features

(1) 25MIPS high-speed pipelined CIP-51 core fully compatible with the 8051 machine.
(2) True 12-bit 100KBps, 8-channel ADC with programmable gain amplifier.
(3) Real 8-bit 500KBps ADC with programmable gain amplifier.
(4) Five 16-bit general purpose timers.
(5) Programmable count/timer array with 5 capture/compare modules.
(6) Internal voltage reference.
(7) Built-in temperature sensor (±3 °C).
(8) On-chip watchdog timer, clock source and VDD monitor.
(9) 64 general purpose digital I/O ports.
(10) It has I2C/SMBUSSPI and two UART and serial interfaces.
(11) 64KB system programmable FLASH memory.
(12) 4352 (4096 + 256) Byte on-chip RAM.
(13) External memory interface of 64 KB address.
(14) The internal FLASH memory can be programmed in the system, either as a program memory or as a non-volatile data memory.
(15) The operating voltage is 2.7V ~ 3.6V, the typical value is 3V, the I / O, RST, JTAG pin allows 5V input voltage.
(16) Full range of industrial grade circuits (-45 ° C - + 85 ° C).
(17) On-chip JTAG emulation circuit, providing full-speed in-circuit emulation, does not occupy on-chip user resources, supports debug commands such as breakpoints, single-step, watchpoint, run and stop, support memory and register checksum modification.

3 internal features

3.1 CPU

The main features of the C8051F020CPU are as follows:

(1) Fully compatible with standard 8051 machines, supporting standard ASM51, KeilC high-level languages;

(2) With high-speed instruction processing capability, the machine cycle is reduced from 12 system clock cycles of the MCS51 standard to one system clock cycle, and 70% of the command time is 1-2 machine cycles, and the command processing capability is greatly improved;

(3) Increased the interrupt source, which is increased from the 7 interrupt sources of the MCS-51 standard to 22 interrupt sources;

(4) The reset source is added. The standard MCS?51 has only external pin reset, and the C8051F020 adds 7 reset sources, which greatly improves the system reliability.

(5) Added a clock source that can work independently in the internal.

3.2 Memory

3.2.1 Data Memory

The C8051F020 has a standard 8051 machine program and data address configuration, including 256 bytes of RAM, of which 128 bytes are high for 2 address spaces, 128 bytes for indirect addressing, and SFR address space for direct addressing. The lower 128 bytes can be accessed by direct or indirect addressing. In addition, the C8051F020 has 4KB of RAM and an external data memory interface (EMIF) located in the external data memory address space. This 4KB RAM can be mapped only to on-chip. It can be mapped to the 64KB external data memory address space, and can be mapped to both on-chip and off-chip (on-chip memory space access within 4KB address, EMIF access over 4KB). The external data memory interface is used to access up to 64KB of external expansion RAM.

3.2.2 Program Memory

The program memory of C8051F020 contains 64KB FLASH. The memory is 512B as one sector. It can be programmed in the system, and there is no need to provide programming voltage outside the chip. The unused sectors of the program memory can be sectorized by the user. Volatile data storage is used.

3.3 I/O and digital crossbar

In addition to the standard 8051 machine ports P0 to P3, the C8051F020 MCU has an additional four 8-bit I/O ports. Thus, the total number of I/O ports can be up to 64, and each port I/O pin can be set to push-pull or open-drain output. The most unique feature is the introduction of a digital crossbar switch that distributes internal digital system resources to the I/O pins of the P0, P1, P2, and P3 ports, as well as on-chip counter/timers, serial buses, and interrupts. The source, A/D conversion input, comparator output, and other digital signals from the microcontroller are configured to be output on the I/O pins above, which allows the user to select general purpose I/O and required digital resources for their particular application. combination.

3.4 Programmable Counting Array

In addition to providing five 16-bit general-purpose timers/counters internally, the C8051F020 also provides an on-chip programmable counter/timer array (PCA). The PCA includes a dedicated 16-bit counter/timer, 5 programmable To capture the compare module, the time reference can be one of the following six clock sources: system clock / 12; system clock / 4; timer 0 overflow; external clock input; system clock and external oscillation frequency / 8. Each capture module has six modes of operation: edge triggered capture, software timer, high speed output, 8-bit pulse width modulator, frequency output, 16-bit pulse width modulator.

3.5 multi-type serial bus port

The C8051F020 has two full-duplex UARTs, SMBUS/I2C bus and SPI bus. Each serial bus is fully implemented in hardware and can generate interrupts to CIP?51. These serial buses do not share timers, interrupts or I. /O port, so users are allowed to use all at the same time.

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