Rainbow Electronics ATmega162V - Manual (Page 110)

110
ATmega162/V
2513E–AVR–09/03
The following code examples show how to do an atomic write of the TCNTn Register
contents. Writing any of the OCRnA/B or ICRn Registers can be done by using the
same principle.
Note: 1. The example code assumes that the part specific header file is included.
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 TCNTn.
Reusing the Temporary High
Byte Register 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.
Assembly Code Example (1)
TIM16_WriteTCNT n :
; Save Global Interrupt Flag
in r18,SREG
; Disable interrupts
cli
; Set TCNT n to r17:r16
out TCNT n H,r17
out TCNT n L,r16
; Restore Global Interrupt Flag
out SREG,r18
ret
C Code Example (1)
void TIM16_WriteTCNT n ( unsigned int i )
{
unsigned char sreg;
unsigned int i;
/* Save Global Interrupt Flag */
sreg = SREG;
/* Disable interrupts */
_CLI();
/* Set TCNT n to i */
TCNT n = i;
/* Restore Global Interrupt Flag */
SREG = sreg;
}