89C51 MCU Timer/Counter 0

The timing counting function of the 89C51 microcontroller is controlled by the special function registers TMOD and TCON.
TMOD has no bit address and cannot perform bit operations. The names and functions of each bit are as follows:
TMOD: GATE C/T1 M1 M0 GATE C/T1 M1 M0
                         D7 D6 D5 D4 D3 D2 D1 D0
 GATE C/T1 M1 M0 controls timing timer 1;
 GATE C/T0 M1 M0 controls timing timer 0;
When GATE=0, the timing counting signal is the state of the T0 pin (P3.4) or the machine cycle (C/T=0 counts the machine cycle, i.e. timing, C/T=1 counts the state of the T0 pin, i.e. counting), and the counting start switch is TR0 (0 turns off counting, 1 starts counting).
When GATE=1, the timing counting function is determined by the T0 pin (P3.4) or the machine cycle (C/T=0 counts the machine cycle, i.e. timing, C/T=1 counts the change state of the T0 pin, i.e. counting), and the counting start switch is determined by TR0 (0 turns off counting, 1 starts counting) and INT0 (pin P3.2).
 M1M0 is the counting mode selection: counting is performed in TH0 and TL0.
 00 is mode 0, 13-bit (8 bits of TH0 and the lower 5 bits of TL0) binary counter, which can count from 0 to 2 to the 13th power -1;
 01 is mode 1, 16-bit binary counter, which can count from 0 to 2 to the 16th power -1;
 10 is mode 2, 8-bit binary counter, TH0 puts the initial value of the count, counting is performed in TL0, and 
                     the initial value in TH0 is automatically loaded into TL0 after overflow;
11 is mode 3, TH0 is an 8-bit counter, and HL0 is an 8-bit counter. The two counters are independent of each other.
T1 and T0 have the same functions.
Special function register TCON can be operated by bit, but generally does not use bit address, but uses bit function name:
Bit address: 8FH 8EH 8DH 8Ch 8Bh 8Ah 89H 88H
TCON: TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 
               D7 D6 D5 D4 D3 D2 D1 D0 
TF0 is T0 count flag: When the timing count overflows, this bit is automatically set to 1, and automatically cleared to 0 after the interrupt count ends.
TR0 is the count switch, when GATE=0, TR0=1 turns on the count, and 0 turns it off. When GATE=1, it controls the counter to open together with INT0, that is, GATE=1, TR0=1, INT0=1 can turn on the count, otherwise it is turned off.
In timing/counting, the value of TH0 TL0 is incremented by 1 and counts to FFFFH. If it is in timing/counting mode, TF0 is set to 1 after overflow and the counting time ends. If it is in interrupt mode, the interrupt request is set to 1 by hardware. After the counting ends, that is, after the interrupt ends, TF0 is automatically cleared to 0.
/***************Timer timing 50ms, 1 second at count 20, display 60 seconds timing (query mode)***********/
#include
#include
#define uchar unsigned char
#define uint unsigned int

void main()
{
  TMOD=0x05;
/*This setting (0000 0101) T0's GATE=0, C/T is 1, M1M0 is 01.
   GATE=0, turn off INT0 (P3.2) pin's control of count start, only TR0 controls start.
    C/T=1, count function, count pin T0 (P3.4) state changes.
   M1M0=01, select counting mode 1, 16-bit binary counter, count from TH0 TL0 to FFFFH, and then overflow. If it is timing/counting mode, TF0 will be set to 1 after overflow, and the counting timing will end. If it is interrupt mode, it will be cleared to 0. Hardware will set TF0 to 1, and the counting will end, that is, the interrupt will end, and TF0 will be automatically cleared to 0. Turn on counter 0 interrupt and set ET0=1, EA=1 */[page]
  TH0=0xff;//Set the initial value of the counter
  TL0=0xfc;//Start counting from the setting here for the first time
  ET0=1;
  TR0=1;
  EA=1;
  while(1)
   {
   P0=yu[k%10];
      delay(1);
      P2=0x01;   
      delay(1);
      P2=0x00;
      P0=yu[k/10];
      delay(1);
      P2=0x02;
      delay(1);
      P2=0x00;   
   }
} /******Count in query mode #include #include #define uchar unsigned char #define uint unsigned int