AT90USB646 datasheet(202/434 Pages) ATMEL

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7593A–AVR–02/06

AT90USB64/128

zero) will not become effective until ongoing and pending transmissions are completed, i.e.,

when the Transmit Shift Register and Transmit Buffer Register do not contain data to be trans-

mitted. When disabled, the Transmitter will no longer override the TxDn port.

• Bit 2 – UCSZn2: Character Size n

The UCSZn2 bits combined with the UCSZn1:0 bit in UCSRnC sets the number of data bits

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

• Bit 1 – RXB8n: Receive Data Bit 8 n

RXB8n is the ninth data bit of the received character when operating with serial frames with nine

data bits. Must be read before reading the low bits from UDRn.

• Bit 0 – TXB8n: Transmit Data Bit 8 n

TXB8n is the ninth data bit in the character to be transmitted when operating with serial frames

with nine data bits. Must be written before writing the low bits to UDRn.

18.9.4

USART Control and Status Register n C – UCSRnC

• Bits 7:6 – UMSELn1:0 USART Mode Select

These bits select the mode of operation of the USARTn as shown in Table 18-4..

Note:

1. See “USART in SPI Mode” on page 207 for full description of the Master SPI Mode (MSPIM)

operation

• Bits 5:4 – UPMn1:0: Parity Mode

These bits enable and set type of parity generation and check. If enabled, the Transmitter will

automatically generate and send the parity of the transmitted data bits within each frame. The

Receiver will generate a parity value for the incoming data and compare it to the UPMn setting.

If a mismatch is detected, the UPEn Flag in UCSRnA will be set.

Bit

UMSELn1

UMSELn0

UPMn1

UPMn0

USBSn

UCSZn1

UCSZn0

UCPOLn

UCSRnC

Read/Write

R/W

Initial Value

Table 18-4.

UMSELn Bits Settings

UMSELn1

UMSELn0

Mode

Asynchronous USART

Synchronous USART

(Reserved)

Master SPI (MSPIM)(1)

Table 18-5.

UPMn Bits Settings

UPMn1

UPMn0

Parity Mode

Disabled

Reserved

Enabled, Even Parity

Enabled, Odd Parity

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