AT90S8515 데이터 시트보기 (PDF) - Atmel Corporation

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AT90S8515

8-bit Microcontroller with 8K Bytes In-System Programmable Flash

Atmel Corporation 

AT90S8515

(TCCR1A and TCCR1B). The interrupt enable/disable settings for Timer/Counter1 are

found in the Timer/Counter Interrupt Mask Register (TIMSK).

When Timer/Counter1 is externally clocked, the external signal is synchronized with the

oscillator frequency of the CPU. To assure proper sampling of the external clock, the

minimum time between two external clock transitions must be at least one internal CPU

clock period. The external clock signal is sampled on the rising edge of the internal CPU

clock.

The 16-bit Timer/Counter1 features both a high-resolution and a high-accuracy usage

with the lower prescaling opportunities. Similarly, the high prescaling opportunities make

the Timer/Counter1 useful for lower speed functions or exact timing functions with infre-

quent actions.

The Timer/Counter1 supports two Output Compare functions using the Output Compare

Register 1 A and B (OCR1A and OCR1B) as the data sources to be compared to the

Timer/Counter1 contents. The Output Compare functions include optional clearing of

the counter on compareA match and actions on the Output Compare pins on both com-

pare matches.

Timer/Counter1 can also be used as an 8-, 9- or 10-bit Pulse Width Modulator. In this

mode, the counter and the OCR1A/OCR1B registers serve as a dual, glitch-free, stand-

alone PWM with centered pulses. Refer to page 47 for a detailed description of this

function.

The Input Capture function of Timer/Counter1 provides a capture of the Timer/Counter1

contents to the Input Capture Register (ICR1), triggered by an external event on the

input capture pin (ICP). The actual capture event settings are defined by the

Timer/Counter1 Control Register (TCCR1B). In addition, the Analog Comparator can be

set to trigger the Input Capture. Refer to “Analog Comparator” on page 59 for details on

this. The ICP pin logic is shown in Figure 31.

Figure 31. ICP Pin Schematic Diagram

If the Noise Canceler function is enabled, the actual trigger condition for the capture

event is monitored over four samples and all four must be equal to activate the capture

flag.

35

0841G–09/01

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