ATmega64A datasheet(114/392 Pages) ATMEL

114 / 392 page

114

8160C–AVR–07/09

ATmega64A

• FOCnA, FOCnB, and FOCnC are added in the new TCCRnC Register.

• WGMn3 is added to TCCRnB.

Interrupt flag and mask bits for Output Compare unit C are added.

The 16-bit Timer/Counter has improvements that will affect the compatibility in some special

cases.

15.3

Accessing 16-bit Registers

The TCNTn, OCRnA/B/C, and ICRn are 16-bit registers that can be accessed by the AVR CPU

via the 8-bit data bus. The 16-bit register must be byte accessed using two read or write opera-

tions. Each 16-bit timer has a single 8-bit register for temporary storing of the high byte of the 16-

bit access. The same temporary register is shared between all 16-bit registers within each 16-bit

timer. Accessing the low byte triggers the 16-bit read or write operation. When the low byte of a

16-bit register is written by the CPU, the high byte stored in the temporary register, and the low

byte written are both copied into the 16-bit register in the same clock cycle. When the low byte of

a 16-bit register is read by the CPU, the high byte of the 16-bit register is copied into the tempo-

rary register in the same clock cycle as the low byte is read.

Not all 16-bit accesses uses the temporary register for the high byte. Reading the OCRnA/B/C

16-bit registers does not involve using the temporary register.

To do a 16-bit write, the high byte must be written before the low byte. For a 16-bit read, the low

byte must be read before the high byte.

The following code examples show how to access the 16-bit timer registers assuming that no

interrupts updates the temporary register. The same principle can be used directly for accessing

the OCRnA/B/C and ICRn Registers. Note that when using “C”, the compiler handles the 16-bit

access.

Note:

1. See “About Code Examples” on page 8.

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

Assembly Code Examples

(1)

; Set TCNT

n to 0x01FF

ldi

r17,0x01

ldi

r16,0xFF

out

TCNT

nH,r17

out

TCNT

nL,r16

; Read TCNT

n into r17:r16

r16,TCNT

r17,TCNT

C Code Examples

(1)

unsigned int

/* Set TCNT

n to 0x01FF */

TCNT

n = 0x1FF;

/* Read TCNT

n into i */

i = TCNT

ATmega64A bảng dữ liệu(PDF) 114 Page - ATMEL Corporation

ATmega64A bảng dữ liệu(HTML) 114 Page - ATMEL Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

bảng dữ liệu tải về

Link URL