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The 8051 microcontroller has two 16-bit timers/counters such as TIMER0 (T0) and TIMER1 (T1). Each timer can be programmed to count internal clock pulses of 8051 microcontroller. These timers are used for the following functions:

  • Calculate time delay between two events
  • Counting the number of events
  • Generate baud rate for serial ports
  • Frequency measurement
  • Pulse width measurement

Generally a timer is used to count machine cycles and provides a specified time delay. Actually a machine cycle consists of 12 oscillator periods. Hence the counting rate is about 133810.png.

Operating Modes

Time Mode 0


The clock frequency input to THx is 133836.png 

Timer/counter logic

Control Registers



Timer/Counter Control(TCON)register 

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