基于vhdl的單總線從機(jī)讀寫控制器(編輯修改稿)
2025-07-23 12:26 本頁面
【文章內(nèi)容簡介】 temp=dq。dq作為輸入（對于控制器來說是輸入，對于DS18b20來說是輸出）21. if(t=580)then22. temp=dq。23. if(temp=39。139。)then如果temp為1說明DS18B20存在（因?yàn)闄z測到了存在脈沖）24. LED=39。039。25. else26. LED=39。139。27. endif。28. endif。1. t=t+1。2. STATE=RESET。3. elsif(t=750)then初始化時序結(jié)束4. t=0。計數(shù)器清零5. STATE=CMD_CC。復(fù)位過程伴隨著忽略rom指令“CC”6. endif。7. whenCMD_CC=忽略rom指令“CC”8. LED2=39。139。9. LED3=39。039。10. write_temp=11001100。將write_temp設(shè)為“11001100”11. STATE=WRITE_BYTE。12. whenWRITE_BYTE=13. caseWRITE_BYTE_CNTis14. when0to7=15. if(write_temp(WRITE_BYTE_CNT)=39。039。)then判斷當(dāng)前write_temp第WRITE_BYTE_CNT上是否為39。039。16. STATE=WRITE_LOW。如果當(dāng)前write_temp第WRITE_BYTE_CNT上是39。039。，進(jìn)入WRITE_LOW狀態(tài)（即對DS18b20寫低）17. LED3=39。139。18. else19. STATE=WRITE_HIGH。如果當(dāng)前write_temp第WRITE_BYTE_CNT上是39。139。，進(jìn)入WRITE_HIGH狀態(tài)（即對DS18b20寫高）20. endif。21. WRITE_BYTE_CNT=WRITE_BYTE_CNT+1。判斷write_temp的下一位22. when8=23. if(WRITE_BYTE_FLAG=0)then第一次寫0XCC完畢24. STATE=CMD_44。25. WRITE_BYTE_FLAG=1。26. elsif(WRITE_BYTE_FLAG=1)then寫0X44完畢27. STATE=RESET。28. WRITE_BYTE_FLAG=2。29. elsif(WRITE_BYTE_FLAG=2)then第二次寫0XCC完畢30. STATE=CMD_BE。31. WRITE_BYTE_FLAG=3。32. elsif(WRITE_BYTE_FLAG=3)then寫0XBE完畢33. STATE=GET_TMP。34. WRITE_BYTE_FLAG=0。35. endif。36. WRITE_BYTE_CNT=0。37. whenothers=STATE=RESET。38. endcase。39. whenWRITE_LOW=進(jìn)入寫0時序，參看前面40. LED3=39。139。41. caseWRITE_LOW_CNTis42. when0=43. dq=39。039。44. if(t=70)then等待時序45. t=0。46. 160
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