ATmega32 Atmel Corporation, ATmega32 Datasheet - Page 152

• Manufacturer Part Number: ATmega32
• Manufacturer: Atmel Corporation

Specifications of ATmega32

• Flash (kbytes): 32 Kbytes
• Pin Count: 44
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 16
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 32
• Ext Interrupts: 3
• Usb Speed: No
• Usb Interface: No
• Spi: 1
• Twi (i2c): 1
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 15
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 2
• Eeprom (bytes): 1024
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 3
• Output Compare Channels: 4
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: Yes
• Calibrated Rc Oscillator: Yes

Receive Compete Flag
and Interrupt
Receiver Error Flags
Parity Checker
2503Q–AVR–02/11
The receive function example reads all the I/O Registers into the Register File before any com-
putation is done. This gives an optimal receive buffer utilization since the buffer location read will
be free to accept new data as early as possible.
The USART Receiver has one flag that indicates the receiver state.
The Receive Complete (RXC) Flag indicates if there are unread data present in the receive buf-
fer. This flag is one when unread data exist in the receive buffer, and zero when the receive
buffer is empty (that is, does not contain any unread data). If the receiver is disabled (RXEN =
0), the receive buffer will be flushed and consequently the RXC bit will become zero.
When the Receive Complete Interrupt Enable (RXCIE) in UCSRB is set, the USART Receive
Complete Interrupt will be executed as long as the RXC Flag is set (provided that global inter-
rupts are enabled). When interrupt-driven data reception is used, the receive complete routine
must read the received data from UDR in order to clear the RXC Flag, otherwise a new interrupt
will occur once the interrupt routine terminates.
The USART Receiver has three Error Flags: Frame Error (FE), Data OverRun (DOR) and Parity
Error (PE). All can be accessed by reading UCSRA. Common for the Error Flags is that they are
located in the receive buffer together with the frame for which they indicate the error status. Due
to the buffering of the Error Flags, the UCSRA must be read before the receive buffer (UDR),
since reading the UDR I/O location changes the buffer read location. Another equality for the
Error Flags is that they can not be altered by software doing a write to the flag location. How-
ever, all flags must be set to zero when the UCSRA is written for upward compatibility of future
USART implementations. None of the Error Flags can generate interrupts.
The Frame Error (FE) Flag indicates the state of the first stop bit of the next readable frame
stored in the receive buffer. The FE Flag is zero when the stop bit was correctly read (as one),
and the FE Flag will be one when the stop bit was incorrect (zero). This flag can be used for
detecting out-of-sync conditions, detecting break conditions and protocol handling. The FE Flag
is not affected by the setting of the USBS bit in UCSRC since the receiver ignores all, except for
the first, stop bits. For compatibility with future devices, always set this bit to zero when writing to
UCSRA.
The Data OverRun (DOR) Flag indicates data loss due to a receiver buffer full condition. A Data
OverRun occurs when the receive buffer is full (two characters), it is a new character waiting in
the receive Shift Register, and a new start bit is detected. If the DOR Flag is set there was one or
more serial frame lost between the frame last read from UDR, and the next frame read from
UDR. For compatibility with future devices, always write this bit to zero when writing to UCSRA.
The DOR Flag is cleared when the frame received was successfully moved from the Shift Regis-
ter to the receive buffer.
The Parity Error (PE) Flag indicates that the next frame in the receive buffer had a parity error
when received. If parity check is not enabled the PE bit will always be read zero. For compatibil-
ity with future devices, always set this bit to zero when writing to UCSRA. For more details see
“Parity Bit Calculation” on page 145
The Parity Checker is active when the high USART Parity mode (UPM1) bit is set. Type of parity
check to be performed (odd or even) is selected by the UPM0 bit. When enabled, the parity
checker calculates the parity of the data bits in incoming frames and compares the result with
the parity bit from the serial frame. The result of the check is stored in the receive buffer together
with the received data and stop bits. The Parity Error (PE) Flag can then be read by software to
check if the frame had a parity error.
The PE bit is set if the next character that can be read from the receive buffer had a parity error
when received and the parity checking was enabled at that point (UPM1 = 1). This bit is valid
until the receive buffer (UDR) is read.
and
“Parity Checker” on page
152.
ATmega32(L)
152