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1 Anonymous Users
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PLL enable 後 UART 就有問題了
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中級會員
 
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各位好
我使用的chip是PIC18F87J50. 剛開始我使用以下的 code, 我的 uart 是可以正常運作的 #define F_OSC 12000000 #define BAUDRATE 9600 #define BRGVAL (F_OSC/16/(BAUDRATE + 1)) TRISCbits.TRISC7 = 1; TRISCbits.TRISC6 = 0; Open1USART( USART_TX_INT_OFF & USART_RX_INT_OFF & USART_ASYNCH_MODE & USART_EIGHT_BIT & USART_CONT_RX & USART_BRGH_HIGH, BRGVAL); while (1) { if (DataRdy1USART()) { c = Read1USART(); if (c == '\r') break; } } 可是當我 enable PLL, 我的 uart 就收不到資料或者是亂碼,是為什麼呢? 這時的頻率該怎麼算呢? 我的外部是 12MHz, 我試過48, 8, 6, ....等頻率. 皆無法運作 #pragma config PLLDIV = 3 // (12 MHz crystal used on this board) #pragma config CPUDIV = OSC1 // OSC1 = divide by 1 mode #pragma config FOSC = HSPLL // Firmware must also set OSCTUNE<PLLEN> to start PLL! #define F_OSC 12000000 #define BAUDRATE 9600 #define BRGVAL (F_OSC/16/(BAUDRATE + 1)) main() { ... ... unsigned int pll_startup_counter = 600; [color=#ff0000]OSCTUNEbits.PLLEN = 1; [/color]//Enable the PLL and wait 2+ms until the PLL locks before enabling USB module while(pll_startup_counter--); TRISCbits.TRISC7 = 1; TRISCbits.TRISC6 = 0; Open1USART( USART_TX_INT_OFF & USART_RX_INT_OFF & USART_ASYNCH_MODE & USART_EIGHT_BIT & USART_CONT_RX & USART_BRGH_HIGH, BRGVAL); while (1) { if (DataRdy1USART()) { c = Read1USART(); if (c == '\r') break; } } }//end main
發表於: 2008/12/1 15:05
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