ATA5773-DK1 Atmel, ATA5773-DK1 Datasheet - Page 97

• Manufacturer Part Number: ATA5773-DK1
• Description: BOARD XMITTER FOR ATA5773 315MHZ
• Manufacturer: Atmel
• Type: Transmitterr

Specifications of ATA5773-DK1

• Frequency: 315MHz
• Maximum Frequency: 315 MHz
• Supply Voltage (max): 4 V
• Supply Voltage (min): 2 V
• Supply Current: 9 mA
• Product: RF Development Tools
• For Use With/related Products: ATA5773
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.16.3
9137E–RKE–12/10
Accessing 16-bit Registers
The TCNT1, OCR1A/B, and ICR1 are 16-bit registers that can be accessed by the AVR
via the 8-bit data bus. The 16-bit register must be byte accessed using two read or write oper-
ations. 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 cop-
ied into the temporary 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 OCR1A/B
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 access-
ing the OCR1A/B and ICR1 Registers. Note that when using “C”, the compiler handles the
16-bit access.
Note:
The assembly code example returns the TCNT1 value in the r17:r16 register pair.
Assembly Code Examples
C Code Examples
...
; Set TCNT1 to 0x01FF
ldi r17,0x01
ldi r16,0xFF
out TCNT1H,r17
out TCNT1L,r16
; Read TCNT1 into r17:r16
in r16,TCNT1L
in r17,TCNT1H
...
unsigned int i;
...
/* Set TCNT1 to 0x01FF */
TCNT1 = 0x1FF;
/* Read TCNT1 into i */
i = TCNT1;
...
1. See
Section 4.6 “About Code Examples” on page
(1)
(1)
Atmel ATA5771/73/74
13.
®
CPU
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