Rainbow Electronics AT90LS4433 - Manual (Page 58)

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AT90S/LS4433
1042G–AVR–09/02
• 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 UDRE is read.
The OR bit is cleared (zero) when data is received and transferred to UDR.
• Bits 2..1 – Res: Reserved Bits
These bits are reserved bits in the AT90S4433 and will always read as zero.
• 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”.
UART Control and Status
Register B – UCSRB
• Bit 7 – RXCIE: RX Complete Interrupt Enable
When this bit is set (one), a setting of the RXC bit in UCSRA will cause the Receive
Complete 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 UCSRA will cause the Transmit
Complete 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 UCSRA 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 7 6 5 4 3 2 1 0
$0A ($2A) RXCIE TXCIE UDRIE RXEN TXEN CHR9 RXB8 TXB8 UCSRB
Read/Write R/W R/W R/W R/W R/W R/W R W
Initial Value 0 0 0 0 0 0 1 0