1、單片機的spi作為從設備進行通信這里運行的實例是單片機作為從設備，采用arm9作為主設備進行spi通信。arm9作為主設備，spi的通信速率最低為500k，單片機采用nec 的78f1166，晶振采用11.0592mhz時spi通信速率可以達到500k。速率匹配上沒有問題。主從設備之間采用的通信協議為dl/645.這里有一個問題，協議的收發數據幀的長度是不確定的。這就涉及到主設備需要讀多少個字節的數據。根據實際應用。645規約實際通信時數據幀不會超過100個字節。所以這里解決的方案是，主設備發送命令后，等待200ms后主設備開始抄讀數據。這里之所以等待200ms，是因為從設備需要準備數據。以下

2、是從設備的應用程序：unsigned char*gpcsi01rxaddress;/* csi01 receive buffer address */unsigned shortgcsi01rxlen;/* csi01 receive data length */unsigned shortgcsi01rxcnt;/* csi01 receive data count */unsigned char*gpcsi01txaddress;/* csi01 send buffer address */unsigned shortgcsi01txlen;/* csi01 send data lengt

3、h */unsigned shortgcsi01txcnt;/* csi01 send data count */#define bufferlen 200unsigned char spi_rx_bufferbufferlen;unsigned char txflag,rxflag;unsigned char data;unsigned long count = 0;void csi01_init( void )/* csi01 initial setting */ st0 |= sau_ch1_stop_trg_on;/* csi01 disable */csimk01 = 1;/* in

4、tcsi01 disable */csiif01 = 0;/* intcsi01 if clear */sir01 = sau_sirmn_fectmn | sau_sirmn_pectmn | sau_sirmn_ovctmn;/* error flag clear */smr01 = sau_smrmn_initialvalue | sau_clock_mode_ti0n | sau_trigger_software | sau_csi | sau_buffer_empty;/sau_transfer_end;scr01 = sau_reception_transmission | sau

5、_timing_4 | sau_msb | sau_length_8;sdr01 = 0;so0&= sau_ch1_data_output_1;/* csi01 so initial level */soe0 |= sau_ch1_output_enable;/* csi01 output enable */* intcsi01 priority low */csipr101 = 0;csipr001 = 0;/* si01 pin setting */pm4 |= 0x10;/* so01 pin setting */p4 |= 0x20;pm4 &= 0x20;/* sck01 pin

6、setting */pm4 |= 0x08;/=void csi01_start( void )csimk01 = 0;/* intcsi01 enable */ss0 |= sau_ch1_start_trg_on;/* csi01 enable */ /gpcsi01rxaddress = spi_rx_buffer;/接收數據指針指向spi_rx_buffer第一個字節 /gcsi01rxcnt = 0;/接收數據個數清零 /gcsi01txcnt = 0;/發送數據個數清零 /setsendflag(sendend);/啟動時處于接收狀態 /setreceiveflag(receivi

7、ng);/啟動后還沒有接收數據/=void csi01_stop( void )st0 |= sau_ch1_stop_trg_on;/* csi01 disable */csimk01 = 1;/* intcsi01 disable */csiif01 = 0;/* intcsi01 if clear */=unsigned char spi_send_data(unsigned char *buffer,unsigned char lenth) gpcsi01txaddress = buffer; gcsi01txcnt = lenth - 1; smr01 |= 0x0001;/add

8、by haolj sio01 = buffer0; setsendflag(sending); while(sendend != check_send_flag() ;/ostimedly(10); return lenth;/=unsigned char spi_receive_data(unsigned char *buffer,unsigned char lenth) unsigned char ack; ack = 0; while(check_receive_flag() = receiving) if(gcsi01rxcnt ack) & gcsi01rxcnt=bufferlen

9、) ack = gcsi01rxcnt; ostimedly(1); else setreceiveflag(receivend); memcpy(buffer,spi_rx_buffer,gcsi01rxcnt); ack = gcsi01rxcnt; gcsi01rxcnt = 0; gpcsi01rxaddress = spi_rx_buffer; return ack; /=#pragma vector = intcsi01_vect_interrupt void md_intcsi01( void ) if( sending = check_send_flag() ) if(gcsi

10、01txcnt = 0) smr01 &= sau_buffer_empty;/add by haolj sio01 = 0xee; setsendflag(sendend); gpcsi01rxaddress = spi_rx_buffer; gcsi01rxcnt = 0; return ; data = sio01; gpcsi01txaddress+;sio01 = *gpcsi01txaddress;gcsi01txcnt-; else data = sio01; sio01 = 0xee; if(gpcsi01rxaddress - spi_rx_buffer) bufferlen

11、) *gpcsi01rxaddress = data; gpcsi01rxaddress +; gcsi01rxcnt +; setreceiveflag(receiving); else setreceiveflag(receivend); gpcsi01rxaddress = spi_rx_buffer; unsigned char check_send_flag(void) return txflag;/=unsigned char check_receive_flag(void) return rxflag;/=void setreceiveflag(unsigned char rflag) rxflag = rflag;/=void sets