![]() The manufacturer labels those as CS02, CS01, and CS00. More specifically, the lowest 3 bits (the last in the 8-bit value) control the prescaler. On that particular Ardiuno, TCCR0B is the register that controls the rate of that particular timer. Let's try to hone in on the line of code you need: TCCR0B=TCCR0B&0b11111000|0x01 To add to Majenko's very thorough and excellent answer (which I can't yet upvote because I'm very newbie): (See sections 14.9.4 OCR0A – Output Compare Register A and 14.9.4 OCR0B – Output Compare Register B in the datasheet) Not to be confused with OCR0A and OCR0B which are two separate numeric values that are compared to the timer's counter value TCNT0 to provide two separate PWM outputs (OC0A as Uno pin D6, and OC0B as Uno pin D5) synchronised from the same timebase. ![]() TCCR0A has bits that control PWM, and TCCR0B has bits that control the timer itself. Or more explicitly so you can see the bits easier: TCCR0B = TCCR0B & 0b11111000 | 0b010 Īs to what the "A" and "B" mean (TCCR0A and TCCR0B), there are two registers that are used to control the timer. So your masking would change to: TCCR0B = TCCR0B & 0b11111000 | 0x02 If you were to set those bits to 010, you'd get "CLK I/O / 8 (From prescaler)". The value that has been masked and created for those three bits is, of course, 001, which in that table is "CLK I/O / (No prescaling)", which is the timer running at the frequency of the IO clock. The three Clock Select bits select the clock source to be used by the Timer/Counter.Īnd a table to show the different meanings of the possible values: The datasheet goes on to tell you what those mean: The second stage, ORing 0x01, then sets CS00 to 1. So the first stage, clearing of the lowest three bits, sets CS02, CS01 and CS00 to 0. Those bits all correspond 1:1 to the binary bits from above in the same order. Section 14.9.2 "TCCR0B – Timer/Counter Control Register B" of the datasheet describes that register in detail. For instance, take the ATMega328P chip from the Arduino UNO board. Now what that actually means with respect to what the TCCR0B register does can be gleaned from the datasheet for the chip. In summary that specific operation clears the lower three bits then sets the lowest bit of TCCR0B. So finally the value is then stored in TCCR0B. Ok, so the next operation is to OR it with 0x01: 01101000Įffectively the two operands have been overlaid on each other and any bits that are set in either operand will be reflected in the result. You can see that the last three bits of the value have been cleared because they aren't 1 in both the left and right operands to the & operator. The first operation is to AND that with 11111000: 01101111 Say the TCCR0B register contains the value 0圆F, which is 157 in decimal, or 01101111 in binary. AND calculates which bits in a pair of binary numbers are both on, and OR calculates which bits in a pair of binary numbers are on in either of the numbers. Incidentally, in decimal that is 248.Ġx01 is hexadecimal for 1 in decimal - it's also 1 in binary.īetween them are bitwise operators - & is a bitwise AND operation, and | is a bitwise OR operation. Put the two together and you have 11111000. It's the same as the hexadecimal number 0xF8. Just because it happens to control one of the timers is besides the point.Ġb11111000 is a binary representation of a value. It could be any variable really - it's just "a value" in this context. Let's break it down into parts: TCCR0B = TCCR0B & 0b11111000 | 0x01 ![]() Means from a pure programming perspective: I need it at 1.įirst I'll tackle what TCCR0B=TCCR0B&0b11111000|0x01 What does those values change relative to the timer. I know that i have here 8 values that i can change from 0 to 1. I now less about the various chips and also about how they implemented the various parameters from arduino ide to work with those chips. Like i said, i'm not very familiar with c++, bits and other stuff regarding the arduino. exists "&" ?Ġb11111000 What is this? i already asked this and the answer was something like "clears the low-order 3 bits". TCCR0B=TCCR0B&0b11111000|0x01 Ġ = Timer1 or 0 call it however you want.ī = What is A,B,C and sometimes D for? What does this?why in that code is the programmer using B and not A,C or D But some specific parameters are hard to understand for me. Just lately i started writing in c++ or a "simplified" c++ in the arduino ide. I normally write web based code(javascript,php.). I need to understand how this works in simple words. Lately i want to rewrite a code(Arduino Uno) to make it work on a Arduino Micro. They also have different timers and different pins which use them. TCCR0B=TCCR0B&0b11111000|0x01 Īs the variuos arduinos have different chips.
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