Atmel ATmega328P Xplained Mini MEGA328P-XMINI MEGA328P-XMINI Data Sheet

117

ATmega48A/PA/88A/PA/168A/PA/328/P [DATASHEET]

Atmel-8271H-AVR- ATmega-Datasheet_08/2014

Note:

1.

For I/O Registers located in extended I/O map, “IN”, “OUT”, “SBIS”, “SBIC”, “CBI”, and “SBI” instructions must 
be replaced with instructions that allow access to extended I/O. Typically “LDS” and “STS” combined with 
“SBRS”, “SBRC”, “SBR”, and “CBR”.

The assembly code example requires that the r17:r16 register pair contains the value to be written to TCNT1.

If writing to more than one 16-bit register where the high byte is the same for all registers written, then the high 
byte only needs to be written once. However, note that the same rule of atomic operation described previously 
also applies in this case.

The Timer/Counter can be clocked by an internal or an external clock source. The clock source is selected by 
the Clock Select logic which is controlled by the Clock Select (CS12:0) bits located in the Timer/Counter control 
Register B

 (TCCR1B). For details on clock sources and prescaler, see 

.

The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional counter unit. 

shows a block diagram of the counter and its surroundings.

Assembly Code Example

TIM16_WriteTCNT

1:

; Save global interrupt flag

r18,SREG

; Disable interrupts

; Set TCNT

1 to r17:r16

TCNT

1H,r17

TCNT

1L,r16

; Restore global interrupt flag

SREG,r18

C Code Example

void TIM16_WriteTCNT

1( unsigned int i )

{

unsigned char sreg;

unsigned int i;

/* Save global interrupt flag */

sreg = SREG;

/* Disable interrupts */

_CLI();

/* Set TCNT

1 to i */

TCNT

1 = i;

/* Restore global interrupt flag */

SREG = sreg;

}