Rainbow Electronics ATmega8515L - Manual (Page 153)

153
ATmega8515(L)
2512A–AVR–04/02
Buffer Register do not contain data to be transmitted. When disabled, the Transmitter
will no longer override the TxD port.
• Bit 2 – UCSZ2: Character Size
The UCSZ2 bits combined with the UCSZ1:0 bit in UCSRC sets the number of data bits
(character size) in a frame the receiver and transmitter use.
• Bit 1 – RXB8: Receive Data Bit 8
RXB8 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 UDR.
• Bit 0 – TXB8: Transmit Data Bit 8
TXB8 is the ninth data bit in the character to be transmitted when operating with serial
frames with 9 data bits. Must be written before writing the low bits to UDR.
USART Control and Status
Register C – UCSRC
The UCSRC Register shares the same I/O location as the UBRRH Register. See the
“Accessing UBRRH/UCSRC Registers” on page 149 which describes how to access
this register.
• Bit 7 – URSEL: Register Select
This bit selects between accessing the UCSRC or the UBRRH Register. It is read as
one when reading UCSRC. The URSEL must be one when writing the UCSRC.
• Bit 6 – UMSEL: USART Mode Select
This bit selects between asynchronous and synchronous mode of operation.
• Bit 5:4 – UPM1:0: Parity Mode
These bits enable and set type of parity generation and check. If enabled, the Transmit-
ter 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 com-
pare it to the UPM0 setting. If a mismatch is detected, the PE flag in UCSRA will be set.
Bit 7 6 5 4 3 2 1 0
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 Value 1 0 0 0 0 1 1 0
Table 63. UMSEL Bit Settings
UMSEL Mode
0 Asynchronous Operation
1 Synchronous Operation