1. 實驗任務 用AT89S51單片機的P0.0/AD0-P0.7/AD7埠接數碼管的a-h端,8位數碼管的S1-S8通過74LS138解碼器的Y0-Y7來控制選通每個數碼管的位選端。AT89S51單片機的P1.0-P1.2控制74LS138的A,B,C端子。在8位數碼管上從右向左循環顯示“12345678”。能夠比較平滑地看到拉幕的效果。 2. 電路原理圖 ͼ4.21.1 3. 系統板上硬體連線 (1. 把“單片機系統”區域中的P0.0/AD0-P0.7/AD7用8芯排線連接到“動態數碼顯示”區域中的a-h埠上; (2. 把“三八解碼模塊”區域中的Y0-Y7用8芯排線連接到“動態數碼顯示”區域中的S1-S8埠上; (3. 把“單片機系統”區域中的P1.0-P1.2埠用3根導線連接到“三八解碼模塊”區域中的A、B、C“埠上; 4. 程序設計方法 (1. 動態數碼顯示技術;如何進行動態掃描,由於一次只能讓一個數碼管顯示,因此,要顯示8位的數據,必須經過讓數碼管一個一個輪流顯示才可以,同時每個數碼管顯示的時間大約在1ms到4ms之間,所以為了保證正確顯示,我必須每隔1ms,就得刷新一個數碼管。而這刷新時間我們採用單片機的定時/計數器T0來控制,每定時1ms對數碼管刷新一次,T0採用方式2。 (2. 在進行數碼顯示的時候,要對顯示單元開闢8個顯示緩衝區,每個顯示緩衝區裝有顯示的不同數據即可。 5. 程序框圖 主程序框圖 中斷服務程序框圖 ͼ4.21.2 6. 彙編源程序 DISPBUF EQU 30H DISPCNT EQU 38H DISPBIT EQU 39H T1CNTA EQU 3AH T1CNTB EQU 3BH CNT EQU 3CH ORG 00H LJMP START ORG 0BH LJMP INT_T0 START: MOV DISPCNT,#8 MOV A,#10 MOV R1,#DISPBUF LP: MOV @R1,A INC R1 DJNZ DISPCNT,LP MOV DISPBIT,#00H MOV T1CNTA,#00H MOV T1CNTB,#00H MOV CNT,#00H MOV TMOD,#01H MOV TH0,#(65536-1000) / 256 MOV TL0,#(65536-1000) MOD 256 SETB TR0 SETB ET0 SETB EA SJMP $ INT_T0: MOV TH0,#(65536-1000) / 256 MOV TL0,#(65536-1000) MOD 256 MOV A,DISPBIT ADD A,#DISPBUF MOV R0,A MOV A,@R0 MOV DPTR,#TABLE MOVC A,@A+DPTR MOV P0,A MOV A,P1 ANL A,#0F8H ADD A,DISPBIT MOV P1,A INC DISPBIT MOV A,DISPBIT CJNE A,#08H,NEXT MOV DISPBIT,#00H NEXT: INC T1CNTA MOV A,T1CNTA CJNE A,#50,LL1 MOV T1CNTA,#00H INC T1CNTB MOV A,T1CNTB CJNE A,#8,LL1 MOV T1CNTB,#00H INC CNT MOV A,CNT CJNE A,#9,LLX MOV CNT,#00H MOV A,CNT LLX: CJNE A,#01H,NEX1 MOV 30H,#8 LL1: LJMP DONE NEX1: CJNE A,#02H,NEX2 MOV 31H,#8 MOV 30H,#8 LJMP DONE NEX2: CJNE A,#03H,NEX3 MOV 32H,#8 MOV 31H,#8 MOV 30H,#8 LJMP DONE NEX3: CJNE A,#04H,NEX4 MOV 33H,#8 MOV 32H,#8 MOV 31H,#8 MOV 30H,#8 LJMP DONE NEX4: CJNE A,#05H,NEX5 MOV 34H,#8 MOV 33H,#8 MOV 32H,#8 MOV 31H,#8 MOV 30H,#8 LJMP DONE NEX5: CJNE A,#06H,NEX6 MOV 35H,#8 MOV 34H,#8 MOV 33H,#8 MOV 32H,#8 MOV 31H,#8 MOV 30H,#8 LJMP DONE NEX6: CJNE A,#07H,NEX7 MOV 36H,#8 MOV 35H,#8 MOV 34H,#8 MOV 33H,#8 MOV 32H,#8 MOV 31H,#8 MOV 30H,#8 LJMP DONE NEX7: CJNE A,#08H,NEX8 MOV 37H,#8 MOV 36H,#8 MOV 35H,#8 MOV 34H,#8 MOV 33H,#8 MOV 32H,#8 MOV 31H,#8 MOV 30H,#8 LJMP DONE NEX8: CJNE A,#00H,DONE MOV 37H,#10 MOV 36H,#10 MOV 35H,#10 MOV 34H,#10 MOV 33H,#10 MOV 32H,#10 MOV 31H,#10 MOV 30H,#10 LL: LJMP DONE DONE: RETI TABLE: DB 3FH,06H,5BH,4FH,66H,6DH,7DH,07H,7FH,6FH,00H END 7. C語言源程序 #include unsigned char code dispcode[]={0x3f,0x06,0x5b,0x4f, 0x66,0x6d,0x7d,0x07, 0x7f,0x6f,0x77,0x7c, 0x39,0x5e,0x79,0x71,0x00}; unsigned char dispbitcode[]={0xf8,0xf9,0xfa,0xfb, 0xfc,0xfd,0xfe,0xff}; unsigned char dispbuf[8]={16,16,16,16,16,16,16,16}; unsigned char dispbitcnt; unsigned int t02scnt; unsigned char t5mscnt; unsigned char u; unsigned char i; void main(void) { TMOD=0x02; TH0=0x06; TL0=0x06; TR0=1; ET0=1; EA=1; while(1); } void t0(void) interrupt 1 using 0 { t5mscnt++; if(t5mscnt==4) { t5mscnt=0; P0=dispcode[dispbuf[dispbitcnt]]; P1=dispbitcode[dispbitcnt]; dispbitcnt++; if(dispbitcnt==8) |