ATtiny167-ESSZ datasheet(90/282 Pages) ATMEL

90 / 282 page

7728D–AVR–07/09

ATtiny87/ATtiny167

Depending on the mode of operation used, the counter is cleared, incremented, or decre-

mented at each timer clock (clk

T0). clkT0 can be generated from an external or internal clock

source, selected by the Clock Select bits (CS02:0). When no clock source is selected (CS02:0

= 0) the timer is stopped. However, the TCNT0 value can be accessed by the CPU, regardless

of whether clk

T0 is present or not. A CPU write overrides (has priority over) all counter clear or

count operations.

The counting sequence is determined by the setting of the WGM01 and WGM00 bits located

in the Timer/Counter Control Register (TCCR0A). There are close connections between how

the counter behaves (counts) and how waveforms are generated on the Output Compare out-

put OC0A. For more details about advanced counting sequences and waveform generation,

see “Modes of Operation” on page 92.

The Timer/Counter Overflow Flag (TOV0) is set according to the mode of operation selected

by the WGM01:0 bits. TOV0 can be used for generating a CPU interrupt.

10.5

Output Compare Unit

The 8-bit comparator continuously compares TCNT0 with the Output Compare Register

(OCR0A). Whenever TCNT0 equals OCR0A, the comparator signals a match. A match will set

the Output Compare Flag (OCF0A) at the next timer clock cycle. If enabled (OCIE0A = 1), the

Output Compare Flag generates an Output Compare interrupt. The OCF0A flag is automati-

cally cleared when the interrupt is executed. Alternatively, the OCF0A flag can be cleared by

software by writing a logical one to its I/O bit location. The Waveform Generator uses the

match signal to generate an output according to operating mode set by the WGM01:0 bits and

Compare Output mode (COM0A1:0) bits. The max and bottom signals are used by the Wave-

form Generator for handling the special cases of the extreme values in some modes of

operation (“Modes of Operation” on page 92).

Figure 10-3 shows a block diagram of the Output Compare unit.

Figure 10-3. Output Compare Unit, Block Diagram

OCFnx (Int.Req.)

= (8-bit Comparator )

OCRnx

OCnx

DATA BUS

TCNTn

WGMn1:0

Waveform Generator

top

FOCn

COMnX1:0

bottom

ATtiny167-ESSZ датащи(PDF) 90 Page - ATMEL Corporation

ATtiny167-ESSZ датащи(HTML) 90 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

датащи скачать

ссылки URL