atmega163l ATMEL Corporation, atmega163l Datasheet - Page 76

• Manufacturer Part Number: atmega163l
• Description: Atmega163 8-bit Avr Microcontroller With 16k Bytes Of In-system Programmable Flash
• Manufacturer: ATMEL Corporation

UART Control and Status
Register B – UCSRB
Baud Rate Generator
76
ATmega163(L)
• Bit 7 – RXCIE: RX Complete Interrupt Enable
When this bit is set (one), a setting of the RXC bit in USR will cause the Receive Com-
plete interrupt routine to be executed provided that global interrupts are enabled.
• Bit 6 – TXCIE: TX Complete Interrupt Enable
When this bit is set (one), a setting of the TXC bit in USR will cause the Transmit Com-
plete interrupt routine to be executed provided that global interrupts are enabled.
• Bit 5 – UDRIE: UART Data Register Empty Interrupt Enable
When this bit is set (one), a setting of the UDRE bit in USR will cause the UART Data
Register Empty interrupt routine to be executed provided that global interrupts are
enabled.
• Bit 4 – RXEN: Receiver Enable
This bit enables the UART Receiver when set (one). When the Receiver is disabled, the
RXC, OR, and FE Status Flags cannot become set. If these flags are set, turning off
RXEN does not cause them to be cleared.
• Bit 3 – TXEN: Transmitter Enable
This bit enables the UART Transmitter when set (one). When disabling the Transmitter
while transmitting a character, the Transmitter is not disabled before the character in the
Shift Register plus any following character in UDR has been completely transmitted.
• Bit 2 – CHR9: 9-bit Characters
When this bit is set (one) transmitted and received characters are 9-bit long plus start
and stop bits. The ninth bit is read and written by using the RXB8 and TXB8 bits in UCR,
respectively. The ninth data bit can be used as an extra stop bit or a parity bit.
• Bit 1 – RXB8: Receive Data Bit 8
When CHR9 is set (one), RXB8 is the ninth data bit of the received character.
• Bit 0 – TXB8: Transmit Data Bit 8
When CHR9 is set (one), TXB8 is the ninth data bit in the character to be transmitted.
The Baud Rate generator is a frequency divider which generates baud-rates according
to the following equation:
•
•
•
Bit
$0A ($2A)
Read/Write
Initial Value
BAUD = Baud Rate
f
UBR = Contents of the UBRRHI and UBRR Registers, (0 - 4095)
CK
= Crystal Clock frequency
RXCIE
R/W
7
0
TXCIE
R/W
6
0
UDRIE
R/W
5
0
BAUD
RXEN
R/W
=
4
0
---------------------------------
16(UBR
f
TXEN
R/W
CK
3
0
+
1
CHR9
R/W
2
0
RXB8
R
1
1
TXB8
W
0
0
1142E–AVR–02/03
UCSRB