The Timer/Counter Control Registers are registers to control timers and counters.
Timer/Counter Control Registers are defined in hardware/tools/avr/avr/include/avr/iom328p.h as below.
#define TCCR0A _SFR_IO8(0x24) #define WGM00 0 #define WGM01 1 #define COM0B0 4 #define COM0B1 5 #define COM0A0 6 #define COM0A1 7 #define TCCR0B _SFR_IO8(0x25) #define CS00 0 #define CS01 1 #define CS02 2 #define WGM02 3 #define FOC0B 6 #define FOC0A 7 #define TCCR1A _SFR_MEM8(0x80) #define WGM10 0 #define WGM11 1 #define COM1B0 4 #define COM1B1 5 #define COM1A0 6 #define COM1A1 7 #define TCCR1B _SFR_MEM8(0x81) #define CS10 0 #define CS11 1 #define CS12 2 #define WGM12 3 #define WGM13 4 #define ICES1 6 #define ICNC1 7 #define TCCR2A _SFR_MEM8(0xB0) #define WGM20 0 #define WGM21 1 #define COM2B0 4 #define COM2B1 5 #define COM2A0 6 #define COM2A1 7 #define TCCR2B _SFR_MEM8(0xB1) #define CS20 0 #define CS21 1 #define CS22 2 #define WGM22 3 #define FOC2B 6 #define FOC2A 7
They call _SFR_IO8() and _SFR_MEM8().