AT90PWM2 datasheet(193/365 Pages) ATMEL

193 / 365 page

193

4317K–AVR–03/2013

AT90PWM2/3/2B/3B

Notes:

1. These transmit functions are written to be general functions. They can be optimized if the con-

tents of the UCSRB is static. For example, only the TXB80 bit of the UCSRB0 Register is used

after initialization.

2. 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 ninth bit can be used for indicating an address frame when using multi processor communi-

cation mode or for other protocol handling as for example synchronization.

18.6.3

Transmitter Flags and Interrupts

The USART Transmitter has two flags that indicate its state: USART Data Register Empty

(UDRE) and Transmit Complete (TXC). Both flags can be used for generating interrupts.

The Data Register Empty (UDRE) flag indicates whether the transmit buffer is ready to receive

new data. This bit is set when the transmit buffer is empty, and cleared when the transmit buffer

contains data to be transmitted that has not yet been moved into the Shift Register. For compat-

ibility with future devices, always write this bit to zero when writing the UCSRA Register.

When the Data Register Empty Interrupt Enable (UDRIE) bit in UCSRB is written to one, the

USART Data Register Empty Interrupt will be executed as long as UDRE is set (provided that

TABLE 4.

Assembly Code Example

(1)(2)

USART_Transmit:

; Wait for empty transmit buffer

sbis

UCSRA,UDRE

rjmp

USART_Transmit

; Copy 9th bit from r17 to TXB80

cbi

UCSRB,TXB80

sbrc

r17,0

sbi

UCSRB,TXB80

; Put LSB data (r16) into buffer, sends the data

sts

UDR,r16

ret

C Code Example(1)(2)

void

USART_Transmit( unsigned int data )

{

/* Wait for empty transmit buffer */

while

( !( UCSRA & (1<<UDRE))) )

;

/* Copy 9th bit to TXB8 */

UCSRB &= ~(1<<TXB80);

if ( data & 0x0100 )

UCSRB |= (1<<TXB80);

/* Put data into buffer, sends the data */

UDR = data;

}

AT90PWM2 Datasheet(PDF) 193 Page - ATMEL Corporation

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