I don't understand why the if statement

dinghao1

I don't understand why the if statement [Copy link]

 

dinghao1

Why does 16 become 15?

1071416541

Paste the entire code... I can't see the P0 value in the first section of the code, but I can see the changing position of sec.

dinghao1

#include

sbit ADDR0 = P1^0; sbit ADDR1 = P1^1; sbit ADDR2 = P1^2; sbit ADDR3 = P1^3; sbit ENLED = P1^4; //Use array to store the truth table of digital tube. Array will be introduced in detail in the next chapter unsigned char code LedChar[] = { 0xC0, 0xF9, 0xA4, 0xB0, 0x99, 0x92, 0x82, 0xF8, 0x80, 0x90, 0x88, 0x83, 0xC6, 0xA1, 0x86, 0x8E }; void main(){ unsigned char cnt = 0; //Record the number of interrupts of T0 unsigned char sec = 0; //Record the number of seconds ENLED = 0; //Enable U3 and select digital tube DS1 ADDR3 = 1; ADDR2 = 0; ADDR1 = 0; ADDR0 = 0; TMOD = 0x01; //Set T0 to mode 1 TH0 = 0xB8; //Assign initial value 0xB800 to T0 TL0 = 0x00; TR0 = 1; //Start T0 while (1){ if (TF0 == 1){ //Judge whether T0 overflows TF0 = 0; //After T0 overflows, clear the interrupt flag TH0 = 0xB8; //And re-assign initial value TL0 = 0x00; cnt++; //Count value increments by 1 if (cnt >= 50){ //Judge whether T0 overflows 50 times cnt = 0; //After reaching 50 times, the count value is cleared P0 = LedChar[sec]; //The value in the truth table corresponding to the current seconds is sent to P0 port sec++; //Seconds record increments by 1 if (sec >= 16){ //When the number of seconds exceeds 0x0F(15), restart from 0 sec = 0; } } } } }

shower.xu

dinghao1 posted on 2017-12-28 17:28 Why does 16 become 15

Array subscripts start at 0, so only up to 15, a total of 16 elements. I also wish the host a happy holiday and progress in learning

ienglgge

In the pcb section, I posted a thread about programming. The thread was a request for help, but it didn't seem to be a request for help.

treesss

In actual use, it can be written as if(++sec>15) { sec=0; } which is shorter

dinghao1

shower.xu posted on 2017-12-29 13:04 Array subscripts start at 0, so they only go up to 15, a total of 16 elements. I also wish the host a happy holiday and progress in learning

dinghao1

shower.xu posted on 2017-12-29 13:04 Array subscripts start at 0, so they only go up to 15, for a total of 16 elements. I also wish the host a happy holiday and good learning

I want to ask why these two are the same

dinghao1

ienglgge posted on 2017-12-29 13:49 In the pcb section, I posted a thread about programming. The post was a help post. It didn't seem to be a help post. .

I will pay attention next time. I don't understand the program I want to ask why

dinghao1

treesss posted on 2017-12-30 18:17 In actual use, it can be written as if(++sec>15) { sec=0; } which is shorter

I don't understand why these two are different, sec>=16 becomes sec>=15

bobde163

dinghao1 posted on 2017-12-28 17:28 Why did 16 become 15

There is something wrong with this description

bioger

dinghao1 posted on 2018-1-2 08:18 I don't understand why these two are different, sec>=16 becomes sec>=15

This is the problem he described