AT80C51RA2 查看數據表（PDF） - Atmel Corporation

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AT80C51RA2

High Performance 8-bit Microcontrollers

Atmel Corporation 

AT/TS8xC51Rx2

11.5.11 External Clock Drive Characteristics (XTAL1)

Symbol

TCLCL

TCHCX

TCLCX

TCLCH

TCHCL

TCHCX/TCLCX

Parameter

Oscillator Period

High Time

Low Time

Rise Time

Fall Time

Cyclic ratio in X2 mode

Min

Max

25

5

5

5

5

40

60

11.5.12 External Clock Drive Waveforms

Figure 11-11. External Clock Drive Waveforms

VCC-0.5 V

0.45 V

0.7VCC

0.2VCC-0.1 V

TCHCL

TCLCX

TCHCX

TCLCH

TCLCL

Units

ns

ns

ns

ns

ns

%

11.5.13 AC Testing Input/Output Waveforms

Figure 11-12. AC Testing Input/Output Waveforms

INPUT/OUTPUT

VCC-0.5 V

0.45 V

0.2VCC+0.9

0.2VCC-0.1

AC inputs during testing are driven at VCC - 0.5 for a logic “1” and 0.45V for a logic “0”. Timing

measurement are made at VIH min for a logic “1” and VIL max for a logic “0”.

11.5.14 Float Waveforms

Figure 11-13. Float Waveforms

FLOAT

VOH-0.1 V VLOAD

VOL+0.1 V

VLOAD+0.1 V

VLOAD-0.1 V

For timing purposes a port pin is no longer floating when a 100 mV change from load voltage

occurs and begins to float when a 100 mV change from the loaded VOH/VOL level occurs. IOL/IOH

≥ ± 20mA.

71

4188F–8051–01/08

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