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HT66FM5440
Brushless DC Motor A/D Flash MCU
HT66FM5440
Brushless DC Motor A/D Flash MCU
Transmitter Empty
Flag TXIF
USR Register
Transmitter Idle
Flag TIDLE
Receiver Overr�n
Flag OERR
Receiver Data
Available RXIF
ADDEN
RX Pin
Wake-�p
WAKE
0
1
0
1
RX� if BNO=0
RX� if BNO=1
UCR� Register
RIE
0
1
TIIE
0
1
TEIE
0
1
UART Interr�pt
Req�est Flag
UARTF
UCR� Register
UARTE
Int_prinE
EMI
0
1
Interr�pt signal
to MCU
UART Interrupt Structure
Address Detect Mode
Setting the Address Detect Mode bit, ADDEN, in the UCR2 register, enables this special mode. If
this bit is enabled then an additional qualifier will be placed on the generation of a Receiver Data
Available interrupt, which is requested by the RXIF flag. If the ADDEN bit is enabled, then when
data is available, an interrupt will only be generated, if the highest received bit has a high value.
Note that the Int_prinE, UARTE and EMI interrupt enable bits must also be enabled for correct
interrupt generation. This highest address bit is the 9th bit if BNO=1 or the 8th bit if BNO=0. If this
bit is high, then the received word will be defined as an address rather than data. A Data Available
interrupt will be generated every time the last bit of the received word is set. If the ADDEN bit
is not enabled, then a Receiver Data Available interrupt will be generated each time the RXIF
flag is set, irrespective of the data last bit status. The address detect mode and parity enable are
mutually exclusive functions. Therefore if the address detect mode is enabled, then to ensure correct
operation, the parity function should be disabled by resetting the parity enable bit PREN to zero.
ADDEN
Bit 9 if BNO=1,
Bit 8 if BNO=0
UART Interrupt
Generated
0
0
√
1
√
1
0
×
1
√
ADDEN Bit Function
UART Power Down and Wake-up
When the UART clock, f
H
, is switched off, the UART will cease to function. If the MCU switches
off the UART clock, f
H
, and enters the power down mode while a transmission is still in progress,
then the transmission will be paused until the UART clock source derived from the microcontroller
is activated. In a similar way, if the MCU switches off the UART clock f
H
and enters the power
down mode by executing the "HALT" instruction while receiving data, then the reception of
data will likewise be paused. When the MCU enters the power down mode, note that the USR,
UCR1, UCR2, transmit and receive registers, as well as the BRG register will not be affected. It
is recommended to make sure first that the UART data transmission or reception has been finished
before the microcontroller enters the power down mode.