11章ccp模块.ppt

第11章CAPTURE/COMPARE/PWMMODULES 11.1 CCP模块基本功能 每个 Capture/Compare/PWM (CCP) 模块包含1个16位寄存器，可作为 ? 捕捉寄存器（Capture register） ? 比较寄存器（Compare register） ? PWM 占空比寄存器（Duty Cycle register） CCP1和CCP2模块是相同，区别仅在于特殊的事件触发。 CCP模块时钟源搭配右表所示： 11.2　CCP模块寄存器、控制寄存器 CCP模块寄存器CCPR CCP1模块－－CCPR1H(16h)、CCPR1L(15h) 特殊事件触发功能：由比较匹配信号产生，并使TMR1复位。 CCP2模块－－CCPR2H(1Ch)、CCPR2L(1Bh) 特殊事件触发功能：由比较匹配信号产生，并使TMR1复位，可启动A/D转换。 CCP控制寄存器CCPCON CCP1模块－－CCPCON1(17h) CCP2模块－－CCPCON2(1Dh) bit 3-0 CCPxM3:CCPxM0: CCPx Mode Select bits 0000 = Capture/Compare/PWM disabled (resets CCPx module) 0100 = Capture mode, every falling edge 0101 = Capture mode, every rising edge 0110 = Capture mode, every 4th rising edge 0111 = Capture mode, every 16th rising edge 1000 = Compare mode, set output (CCPX PIN) on match (CCPxIF bit is set) 1001 = Compare mode, clear output （CCPX PIN ）on match (CCPxIF bit is set) 1010 = Compare mode, generate software interrupt on match (CCPxIF bit is set, CCPx pin is unaffected) 1011 = Compare mode, trigger special event (CCPxIF bit is set, CCPx pin is unaffected); CCP1 resets TMR1; CCP2 resets TMR1 and starts an A/D conversion (if A/D module is enabled) 11xx = PWM mode bit 5-4 CCPxX:CCPxY: PWM Least Significant bits Capture mode:Unused. Compare mode:Unused. PWM mode:These bits are the two LSbs of the PWM duty cycle. The eight MSbs are found in CCPRxL. 11.3 Capture Mode In Capture mode, CCPR1H:CCPR1L captures the 16-bit value of the TMR1 register when an event occurs on pin RC2/CCP1. An event is defined as one of the following: ? Every falling edge ? Every rising edge ? Every 4th rising edge ? Every 16th rising edge The type of event is configured by control bits, CCP1M3:CCP1M0 (CCPxCON3:0). When a capture is made, the interrupt request flag bit, CCP1IF (PIR12), is set. The interrupt flag must be cleared in software. If another capture occurs before the value in register CCPR1 is read, the old captured value is overwritten by the new value. 11.3.1 CCP PIN CONFIGURATION In Capture mode, the RC2/C