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Datenblatt-Suchmaschine für elektronische Bauteile |
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Datenblatt-Suchmaschine für elektronische Bauteile |
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STC89LE53RC Datenblatt(PDF) 89 Page - STCmicro Technology Co,.Ltd |
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STC89LE53RC Datenblatt(HTML) 89 Page - STCmicro Technology Co,.Ltd |
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89 / 165 page  Chapter 7 Timer/Counter STC89xx has three 16-bit timers, and they are named T0, T1 and T2. Each of them can also be individually configured as timers or event counters. In the “Timer” function, the register is incremented every 12 system clocks or 6 system clocks depending on 12T mode or 6T mode that the user configured this device. In the “Counter” function, the register is incremented in response to a 1-to-0 transition at its corresponding external input pin, T0,T1 or T2. In this function, the external input is sampled once at the positive edge of every clock cycle. When the samples show a high in one cycle and a low in the next cycle, the count is incremented. The new count value appears in the register at the end of the cycle following the one in which the transition was detected. Since it takes 2 machine cycles(24 system clocks) to recognize a l-to-0 transition, the maximum count rate is 1/24 of the system clock. There are no restrictions on the duty cycle of the external input signal, but to ensure that a given level is sampled at least once before it changes, it should be held for at least one full machine cycle. The “Timer” or “Counter” function of Timer 0 and Timer 1 is selected by control bits C/T in the Speciai Function Register TMOD. And the “Timer” or “Counter” function of Timer 2 is selected by control bit C/T2 in the Speciai Function Register T2CON. There are two SFR designed to configure timers T0 and T1. They are TMOD, TCON. There are extra two SFR designed to configure timer T2. They are T2MOD, T2CON. Symbol Description Address Bit Address and Symbol MSB LSB Value after Power-on or Reset TCON Timer Control 88H TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0 0000 0000B TMOD Timer Mode 89H GATE C/T M1 M0 GATE C/T M1 M0 0000 0000B TL0 Timer Low 0 8AH 0000 0000B TL1 Timer Low 1 8BH 0000 0000B TH0 Timer High 0 8CH 0000 0000B TH1 Timer High 1 8DH 0000 0000B T2CON Timer/Counter 2 control C8H TF2 EXF2 RCLK TCLK EXEN2 TR2 C/T2 CP/RL2 0000 0000B T2MOD Timer/Counter 2 mode C9H ------ T2OE DCEN xxxx xx00B RCAP2L Timer/Counter 2 Reload/ Capture High Byte CAH 0000 0000B RCAP2H Timer/Counter 2 Reload/ Capture High Byte CBH 0000 0000B TL2 Timer/Counter 2 Low Byte CCH 0000 0000B TH2 Timer/Counter 2 High Byte CDH 0000 0000B 89 |
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