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--- en:avr:timers [2010/11/29 08:19] – allan.pettai
+++ en:avr:timers [2020/07/20 09:00] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 ====== Counters/Timers ======
-Counters, which in some sense can be called timers, are one of the most important sub-functions of a microcontroller. These enable to precisely time processes, generate signals and count events. A counter converts the number of input cycles to a binary value using an array of triggers. The maximum number of counted cycles depends on the length of this array and this is marked by the length of the binary code. AVR has 8- and 16-bit counters. If a timer has reached its maximum value (255 in 8-bit and 65535 in 16-bit counters), the next cycle will generate an overflow and the counter resets back to 0. A counter's clock signal can come from the clock signal of the microcontroller, and in this case it is possible to decrease its value using a prescaler. Some AVRs have an internal independent clock signal generator, which can be modified to run faster using a frequency multiplier. Counters also differ in application cases and work modes.
+Counters, which in some sense can be called timers, are one of the most important sub-functions of a microcontroller. These enable to precisely time processes, generate signals and count events. A counter converts the number of input cycles to a binary value using an array of triggers. The maximum number of counted cycles depends on the length of this array, and this is marked by the length of the binary code. AVR has 8- and 16-bit counters. If a timer has reached its maximum value (255 in 8-bit and 65535 in 16-bit counters), the next cycle will generate an overflow and the counter resets back to 0. A counter's clock signal can come from the clock signal of the microcontroller, and in this case it is possible to decrease its value using a prescaler. Some AVRs have an internal independent clock signal generator, which can be modified to run faster using a frequency multiplier. Counters also differ in application cases and work modes.
 ===== Counter's Default Mode =====
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 </code>
-The counter in this example will not generate the interrupt in exactly 10 ms though, in order to do that it would require giving the counter a decimal value and this is not possible. To achieve a precise interval between the interrupts, both the prescaler value and the initial value of the counter have to be chosen so that their division results in an exact number. This is not always possible, especially with 8-bit counters as their value range is quite small. To achieve a more precise or larger interval, a 16-bit counter can be used.
+The counter in this example will not generate the interrupt in exactly 10 ms, though, in order to do that it would require giving the counter a decimal value, and this is not possible. To achieve a precise interval between the interrupts, both the prescaler value and the initial value of the counter have to be chosen so that their division results in an exact number. This is not always possible, especially with 8-bit counters as their value range is quite small. To achieve a more precise or larger interval, a 16-bit counter can be used.
 </box>
@@ Line 70: / Line 70: @@
 	// The result is valid only if the counter
-	// has not overflown yet
+	// has not overflowed yet
 	if (!(TIFR & (1 << TOV1)))
 	{
@@ Line 111: / Line 111: @@
 ===== Signal Generating =====
-More complex counters can generate a signal, in addition to timing the length of one. For this purpose the counter has an output compare unit and a compare match output unit. The output compare unit has registers with the same bit-width as the counter and the values of these registers are compared to the value of the counter while it is running. An interrupt can be generated and special pins' values can be changed each time the counter's value is equal to the value in the compare unit register. At this moment a pin can either be set high or low or inversed. The signal is generated by changes in the value of the output pin.
+More complex counters can generate a signal, in addition to timing the length of one. For this purpose the counter has an output compare unit and a compare match output unit. The output compare unit has registers with the same bit-width as the counter and the values of these registers are compared to the value of the counter while it is running. An interrupt can be generated and special pins' values can be changed each time the counter's value is equal to the value in the compare unit register. At this moment a pin can either be set high, low or inversed. The signal is generated by changes in the value of the output pin.
 In some signal generating modes, the counter's maximum value can be altered. The counter's physical size will remain the same, but a comparison register is used to reset the counter at a specific count. The previous examples could also be solved by using this method, but the function is rather for changing the period of the signal. In addition to this, a counter can be configured to a mode where it works with both incrementing and decrementing.
@@ Line 123: / Line 123: @@
 <box 100% round #EEEEEE|Example>
-Task: using an 8MHz ATmega128, generate two speed regulating servo motor signals. Use pin PB5 (OC1A) to generate a pulse width of 1 ms and pin PB6 (OC1B) to generate pulse width of 2 ms.
+Task: Using an 8MHz ATmega128, generate two speed regulating servo motor signals. Use pin PB5 (OC1A) to generate a pulse width of 1 ms and pin PB6 (OC1B) to generate pulse width of 2 ms.
 <code c>

en/avr/timers.1291018789.txt.gz · Last modified: 2020/07/20 09:00 (external edit)