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8051 Aula 02

8051 Aula 02. Prof Afonso Ferreira Miguel. Microcontrolador 8051 (MCS-51). Timers do MCS51 Two 16-bit Counter/Timers: Up counters, can interrupt on overflow. Counts: CPU cycles (crystal/12). External input (max. half CPU rate). Four Operation Modes. Microcontrolador 8051 (MCS-51).

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8051 Aula 02

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  1. 8051Aula 02 Prof Afonso Ferreira Miguel

  2. Microcontrolador 8051 (MCS-51) • Timers do MCS51 • Two 16-bit Counter/Timers: Up counters, can interrupt on overflow. • Counts: CPU cycles (crystal/12). External input (max. half CPU rate). • Four Operation Modes.

  3. Microcontrolador 8051 (MCS-51) • Timers do MCS51 • Timer Mode 0 : Emulates 8048 counter/timer (13-bits). 8-bit counter (TL0 or TL1). 5-bit prescaler (TH0 or TH1). • Timer Mode 1 : Simple 16-bit counter. • Timer Mode 2 : 8-bit auto-reload. Counter in TL0 or TL1. Reload value in TH0 or TH1. Provides a periodic flag or interrupt.

  4. Microcontrolador 8051 (MCS-51) • Timers do MCS51 • Timer Mode 3 : • Splits timer 0 into two 8-bit counter/timers. • First counter (TLO) acts like mode 0, • without prescaler. • Second counter (TH0): • Counts CPU cycles. • Uses TR1 (timer 1 run bit) as enable. • Uses TF1 (timer 1 overflow bit) as flag. • Uses Timer 1 interrupt. • Timer 1 (when timer 0 is in mode 3 ): • Counter stopped if in mode 3. • Running in mode 0, 1, or 2. • Has gate (INT1) and external input (T1), but no flag or interrupt. • May be used as a baud rate generator.

  5. C/T=0 C/T=1 Microcontrolador 8051 (MCS-51) • Timers do MCS51 – MODO 1 Osc. Osc. ÷12 Interrupt TL1 TH1 TF1 8-bits 8-bits T1 (Pin) Control TR1 Gate INT1 (Pin) The Gate input controls whether the Counter runs while gated by the interrupt signal or not.

  6. C/T=0 TH1 C/T=1 8-bits Microcontrolador 8051 (MCS-51) • Timers do MCS51 – MODO 2 Osc. Osc. ÷12 Interrupt TL1 TF1 8-bits T1 (Pin) Control TR1 Gate INT1 (Pin) The Gate input controls whether the Counter runs while gated by the interrupt signal or not.

  7. Microcontrolador 8051 (MCS-51) • Timers do MCS51 – TMOD

  8. Microcontrolador 8051 (MCS-51) • Timers do MCS51 – TCON

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