ATEMGA128-16AI View Datasheet(PDF) - Atmel Corporation

Part Name

Description

MFG CO.

ATEMGA128-16AI

8-bit Microcontroller with 128K Bytes In-System Programmable Flash

Atmel Corporation 

Prev 111 112 113 114 115 116 117 118 119 120 Next

ATmega128

code updates the temporary register by accessing the same or any other of the 16-bit

Timer Registers, then the result of the access outside the interrupt will be corrupted.

Therefore, when both the main code and the interrupt code update the temporary regis-

ter, the main code must disable the interrupts during the 16-bit access.

The following code examples show how to do an atomic read of the TCNTn Register

contents. Reading any of the OCRnA/B/C or ICRn Registers can be done by using the

same principle.

Assembly Code Example(1)

TIM16_ReadTCNTn:

; Save global interrupt flag

in r18,SREG

; Disable interrupts

cli

; Read TCNTn into r17:r16

in r16,TCNTnL

in r17,TCNTnH

; Restore global interrupt flag

out SREG,r18

ret

C Code Example(1)

unsigned int TIM16_ReadTCNTn( void )

{

unsigned char sreg;

unsigned int i;

/* Save global interrupt flag */

sreg = SREG;

/* Disable interrupts */

__disable_interrupt();

/* Read TCNTn into i */

i = TCNTn;

/* Restore global interrupt flag */

SREG = sreg;

return i;

}

Note: 1. See “About Code Examples” on page 9.

The assembly code example returns the TCNTn value in the r17:r16 register pair.

2467O–AVR–10/06

115

Share Link: