ATtiny261-ESSZ datasheet(112/227 Pages) ATMEL

112 / 227 page

112

7753C–AVR–07/09

ATtiny261/ATtiny461/ATtiny861

16.10 Accessing 10-Bit Registers

If 10-bit values are written to the TCNT1 and OCR1A/B/C/D registers, the 10-bit registers can be

byte accessed by the AVR CPU via the 8-bit data bus using two read or write operations. The

10-bit registers have a common 2-bit Timer/Counter1 High Byte Register (TC1H) that is used for

temporary storing of the two MSBs of the 10-bit access. The same TC1H register is shared

between all 10-bit registers. Accessing the low byte triggers the 10-bit read or write operation.

When the low byte of a 10-bit register is written by the CPU, the high byte stored in the TC1H

When the low byte of a 10-bit register is read by the CPU, the high byte of the 10-bit register is

copied into the TC1H register in the same clock cycle as the low byte is read.

To do a 10-bit write, the high byte must be written to the TC1H register before the low byte is

written. For a 10-bit read, the low byte must be read before the high byte.

The following code examples show how to access the 10-bit timer registers assuming that no

interrupts updates the TC1H register. The same principle can be used directly for accessing the

OCR1A/B/C/D registers.

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 returns the TCNT1 value in the r17:r16 register pair.

Assembly Code Example

...

; Set TCNT

1 to 0x01FF

ldi

r17,0x01

ldi

r16,0xFF

out

1H,r17

out

TCNT

1,r16

; Read TCNT

1 into r17:r16

r16,TCNT

r17,TC

...

C Code Example

unsigned int

...

/* Set TCNT1 to 0x01FF */

TC1H = 0x01;

TCNT1 = 0xFF;

/* Read TCNT1 into i */

i = TCNT1;

i |= ((unsigned int)TC1H << 8);

...

ATtiny261-ESSZ Scheda tecnica(PDF) 112 Page - ATMEL Corporation

ATtiny261-ESSZ Scheda tecnica(HTML) 112 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

Scheda tecnica Scarica

Link URL