The document discusses the timers/counters of the 8051 microcontroller. It describes: 1) The two timers/counters - timer/counter 0 and timer/counter 1 that can be used as timers or event counters. 2) How the timers work using internal clock pulses to count up and trigger interrupts when they overflow. 3) The timer mode and control registers that are used to configure the timers for different modes and start/stop them. 4) Examples of using the timers to generate delays and square waves for applications like measuring wheel rotations.

13. TCON: Timer/Counter Control Register For timer 0 SETB TR0 = SETB TCON.4 CLR TR0 = CLR TCON.4 SETB TF0 = SETB TCON.5 CLR TF0 = CLR TCON.5 For timer 1 SETB TR1 = SETB TCON.6 CLR TR1 = CLR TCON.6 SETB TF1 = SETB TCON.7 CLR TF1 = CLR TCON.7 TF1 IT0 IE0 IT1 IE1 TR0 TF0 TR1

18. XTAL oscillator ÷ 12 TR TH TL TF Timer overflow flag C/T = 0 TF goes high when FFFF 0