Rainbow-electronics ATmega8515L Manuel d'utilisateur télécharger pdf (Page 153)

153

ATmega8515(L)

2512A–AVR–04/02

Buffer Registerdonotcontain data to betransmitted. When disabled, theTransmitter

will no longer overridetheTxD port.

• Bit 2 – UCSZ2: Character Size

The UCSZ2 bitscombinedwith the UCSZ1:0 bit in UCSRCsets the number ofdata bits

(charactersize) in a frame the receiver and transmitter use.

• Bit1–RXB8: Receive Data Bit 8

RXB8is theninthdata bit of the receivedcharacterwhen operating withserialframes

with nine data bits. Must be readbefore reading the lowbitsfrom UDR.

• Bit0–TXB8:TransmitDataBit8

TXB8is theninthdata bit in the character to betransmittedwhen operating withserial

frameswith9data bits. Must be written before writing the lowbits to UDR.

USART Control and Status

The UCSRC Registershares the same I/Olocation as the UBRRH Register. See the

“Accessing UBRRH/UCSRC Registers”onpage 149which describeshow to access

thisregister.

• Bit 7 – URSEL: Register Select

Thisbit selectsbetween accessing the UCSRC or the UBRRH Register. Itisread as

one when reading UCSRC.The URSEL must be one when writing the UCSRC.

• Bit 6 – UMSEL: USART Mode Select

Thisbit selectsbetween asynchronous andsynchronous modeof operation.

• Bit 5:4 – UPM1:0: Parity Mode

These bits enableandset typeofparity generation andcheck. If enabled, theTransmit-

terwill automatically generate andsend the parity of thetransmitteddata bitswithin

each frame. TheReceiverwill generate a parity value for theincoming data andcom-

pareittothe UPM0 setting. If amismatch isdetected, thePEflag in UCSRA will be set.

Bit 76543 210

URSEL UMSEL UPM1 UPM0 USBS UCSZ1 UCSZ0 UCPOL UCSRC

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

Initial Value10000110

Table 63. UMSEL Bit Settings

UMSEL Mode

0AsynchronousOperation

1 SynchronousOperation

1 2 ... 148 149 150 151 152 153 154 155 156 157 158 ... 222 223

Pas de commentaire

Rainbow-electronics ATmega8515L Manuel d'utilisateur Page 153