atmega163l ATMEL Corporation, atmega163l Datasheet - Page 75

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

ATmega163(L)
When the TXCIE bit in UCR is set, setting of TXC causes the UART Transmit Complete
interrupt to be executed. TXC is cleared by hardware when executing the corresponding
interrupt handling vector. Alternatively, the TXC bit is cleared (zero) by writing a logical
one to the bit.
• Bit 5 – UDRE: UART Data Register Empty
This bit is set (one) when a character written to UDR is transferred to the Transmit Shift
Register. Setting of this bit indicates that the transmitter is ready to receive a new char-
acter for transmission.
When the UDRIE bit in UCR is set, the UART Transmit Complete interrupt to be exe-
cuted as long as UDRE is set. UDRE is cleared by writing UDR. When interrupt-driven
data transmittal is used, the UART Data Register Empty Interrupt routine must write
UDR in order to clear UDRE, otherwise a new interrupt will occur once the interrupt rou-
tine terminates.
UDRE is set (one) during reset to indicate that the transmitter is ready.
• Bit 4 – FE: Framing Error
This bit is set if a Framing Error condition is detected, i.e. when the stop bit of an incom-
ing character is zero.
The FE bit is cleared when the stop bit of received data is one.
• Bit 3 – OR: OverRun
This bit is set if an Overrun condition is detected, i.e., when a character already present
in the UDR Register is not read before the next character has been shifted into the
Receiver Shift Register. The OR bit is buffered, which means that it will be set once the
valid data still in UDR is read.
The OR bit is cleared (zero) when data is received and transferred to UDR.
• Bit 2 – Res: Reserved Bit
This bit is a reserved bit in the ATmega163 and will always read as zero.
• Bits 1 – U2X: Double the UART Transmission Speed
Setting this bit will reduce the division of the baud rate generator clock from 16 to 8,
effectively doubling the transfer speed at the expense of robustness. For a detailed
description, see “Double Speed Transmission” on page 78.
• Bit 0 – MPCM: Multi-processor Communication Mode
This bit is used to enter Multi-Processor Communication mode. The bit is set when the
slave MCU waits for an address byte to be received. When the MCU has been
addressed, the MCU switches off the MPCM bit, and starts data reception.
For a detailed description, see “Multi-processor Communication Mode” on page 73.
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