Microchip 公司的PIC18F2585/2680/4585/4680是 28/40/44引腳的增強(qiáng)型閃存微控制器，具有ECAN™和nanoWatt技術(shù)以及10位ADC，適合許多高性能和對(duì)功耗敏感的應(yīng)用。本文介紹了PIC18F 2680和PIC18F 4680在汽車輪胎監(jiān)測(cè)系統(tǒng)（TPMS）的應(yīng)用。首先介紹了PIC18F 2680和PIC18F 4680的主要性能和方框圖，接著介紹了APGRD003 汽車輪胎監(jiān)測(cè)系統(tǒng)（TPMS）的主要電路。
APGRD003 Tire Pressure Measurement System
PIC18F2585/2680/4585/4680 28/40/44-Pin Enhanced Flash Microcontrollers with
ECAN Technology, 10-Bit A/D and nanoWatt Technology

Power Managed Modes:

Run: CPU on, peripherals on
Idle: CPU off, peripherals on
Sleep: CPU off, peripherals off
Idle mode currents down to 5.8 A typical
Sleep mode currents down to 0.1 A typical
Timer1 Oscillator: 1.1 A, 32 kHz, 2V
Watchdog Timer: 2.1 A
Two-Speed Oscillator Start-up
Flexible Oscillator Structure:
Four Crystal modes, up to 40 MHz
4x Phase Lock Loop (PLL) – available for crystal and internal oscillators
Two External RC modes, up to 4 MHz
Two External Clock modes, up to 40 MHz
Internal oscillator block:
8 user selectable frequencies, from 31 kHz to 8 MHz
Provides a complete range of clock speeds, from 31 kHz to 32 MHz when used with PLL
User tunable to compensate for frequency drift
Secondary oscillator using Timer1 @ 32 kHz
Fail-Safe Clock Monitor
Allows for safe shutdown if peripheral clock stops
Special Microcontroller Features:
C compiler optimized architecture with optional extended instruction set
100,000 erase/write cycle Enhanced Flash program memory typical
1,000,000 erase/write cycle Data EEPROM memory typical
Flash/Data EEPROM Retention: > 40 years
Self-programmable under software control
Priority levels for interrupts
8 x 8 Single Cycle Hardware Multiplier
Extended Watchdog Timer (WDT):
Programmable period from 41 ms to 131s
Single-Supply 5V In-Circuit Serial Programming™ (ICSP™) via two pins
In-Circuit Debug (ICD) via two pins
Wide operating voltage range: 2.0V to 5.5V
Peripheral Highlights:
High current sink/source 25 mA/25 mA
Three external interrupts
One Capture/Compare/PWM (CCP1) module
Enhanced Capture/Compare/PWM (ECCP1) module (40/44-pin devices only):
One, two or four PWM outputs
Selectable polarity
Programmable dead time
Auto-Shutdown and Auto-Restart
Master Synchronous Serial Port (MSSP) module supporting 3-wire SPI (all 4 modes) and I2C™ Master and Slave modes
Enhanced Addressable USART module:
Supports RS-485, RS-232 and LIN 1.3
RS-232 operation using internal oscillator block (no external crystal required)
Auto-Wake-up on Start bit
Auto-Baud Detect
10-bit, up to 11-channel Analog-to-Digital Converter module (A/D), up to 100 Ksps
Auto-acquisition capability
Conversion available during Sleep
Dual analog comparators with input multiplexing
ECAN Module Features:
Message bit rates up to 1 Mbps
Conforms to CAN 2.0B ACTIVE Specification
Fully backward compatible with PIC18XXX8 CAN modules
Three modes of operation:
Legacy, Enhanced Legacy, FIFO
Three dedicated transmit buffers with prioritization
Two dedicated receive buffers
Six programmable receive/transmit buffers
Three full 29-bit acceptance masks
16 full 29-bit acceptance filters w/ dynamic association
DeviceNet™ data byte filter support
Automatic remote frame handling
Advanced error management features

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圖1.PIC18F2585/2680 (28引腳)方框圖

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圖2.PIC18F4585/4680 (40/44引腳)方框圖

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圖3.TPMS LF Initiator

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圖4.TPMS Base Station（1）

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圖5.TPMS Base Station（2）

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圖6.TPMS Sensor Transponder