Rainbow-electronics ATtiny2313 Manual de usuario descargar pdf (Pagina 135)

135

ATtiny2313

2543A–AVR–08/03

• Bit 2:1 – UCSZ1:0: Character Size

The UCSZ1:0 bits combined with the UCSZ2 bit in UCSRB sets the number of data bits

(Character SiZe) in a frame the Receiver and Transmitter use.

• Bit 0 – UCPOL: Clock Polarity

This bit is used for synchronous mode only. Write this bit to zero when asynchronous

mode is used. The UCPOL bit sets the relationship between data output change and

data input sample, and the synchronous clock (XCK).

USART Baud Rate Registers –

UBRRL and UBRRH

• Bit 15:12 – Reserved Bits

These bits are reserved for future use. For compatibility with future devices, these bit

must be written to zero when UBRRH is written.

• Bit 11:0 – UBRR11:0: USART Baud Rate Register

This is a 12-bit register which contains the USART baud rate. The UBRRH contains the

four most significant bits, and the UBRRL contains the eight least significant bits of the

USART baud rate. Ongoing transmissions by the Transmitter and Receiver will be cor-

rupted if the baud rate is changed. Writing UBRRL will trigger an immediate update of

the baud rate prescaler.

Table 55. UCSZ Bits Settings

UCSZ2 UCSZ1 UCSZ0 Character Size

0 0 0 5-bit

0 0 1 6-bit

0 1 0 7-bit

0 1 1 8-bit

100Reserved

101Reserved

110Reserved

1 1 1 9-bit

Table 56. UCPOL Bit Settings

UCPOL

Transmitted Data Changed (Output of

TxD Pin)

Received Data Sampled (Input on

RxD Pin)

0 Rising XCK Edge Falling XCK Edge

1 Falling XCK Edge Rising XCK Edge

Bit 151413121110 9 8

– – – – UBRR[11:8] UBRRH

UBRR[7:0] UBRRL

76543210

Read/Write R R R R R/W R/W R/W R/W

R/W R/W R/W R/W R/W R/W R/W R/W

Initial Value00000000

00000000

1 2 ... 130 131 132 133 134 135 136 137 138 139 140 ... 210 211

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