SAM3N4B Atmel Corporation, SAM3N4B Datasheet - Page 508
SAM3N4B
Manufacturer Part Number
SAM3N4B
Description
Manufacturer
Atmel Corporation
Specifications of SAM3N4B
Flash (kbytes)
256 Kbytes
Pin Count
64
Max. Operating Frequency
48 MHz
Cpu
Cortex-M3
# Of Touch Channels
32
Hardware Qtouch Acquisition
No
Max I/o Pins
79
Ext Interrupts
79
Quadrature Decoder Channels
2
Usb Speed
No
Usb Interface
No
Spi
3
Twi (i2c)
2
Uart
4
Ssc
1
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
10
Adc Resolution (bits)
10
Adc Speed (ksps)
384
Resistive Touch Screen
No
Dac Channels
1
Dac Resolution (bits)
10
Temp. Sensor
No
Crypto Engine
No
Sram (kbytes)
24
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
No
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8/3.3
Operating Voltage (vcc)
1.62 to 3.6
Fpu
No
Mpu / Mmu
no / no
Timers
6
Output Compare Channels
6
Input Capture Channels
3
Pwm Channels
4
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes
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29.5.2.2
29.5.2.3
508
508
SAM3N
SAM3N
Start Detection and Data Sampling
Receiver Ready
The programmer can also put the receiver in its reset state by writing UART_CR with the bit
RSTRX at 1. In doing so, the receiver immediately stops its current operations and is disabled,
whatever its current state. If RSTRX is applied when data is being processed, this data is lost.
The UART only supports asynchronous operations, and this affects only its receiver. The UART
receiver detects the start of a received character by sampling the URXD signal until it detects a
valid start bit. A low level (space) on URXD is interpreted as a valid start bit if it is detected for
more than 7 cycles of the sampling clock, which is 16 times the baud rate. Hence, a space that is
longer than 7/16 of the bit period is detected as a valid start bit. A space which is 7/16 of a bit
period or shorter is ignored and the receiver continues to wait for a valid start bit.
When a valid start bit has been detected, the receiver samples the URXD at the theoretical mid-
point of each bit. It is assumed that each bit lasts 16 cycles of the sampling clock (1-bit period)
so the bit sampling point is eight cycles (0.5-bit period) after the start of the bit. The first sampling
point is therefore 24 cycles (1.5-bit periods) after the falling edge of the start bit was detected.
Each subsequent bit is sampled 16 cycles (1-bit period) after the previous one.
Figure 29-3. Start Bit Detection
Figure 29-4. Character Reception
When a complete character is received, it is transferred to the UART_RHR and the RXRDY sta-
tus bit in UART_SR (Status Register) is set. The bit RXRDY is automatically cleared when the
receive holding register UART_RHR is read.
Sampling Clock
Baud Rate
Example: 8-bit, parity enabled 1 stop
Sampling
URXD
Clock
URXD
0.5 bit
period
True Start Detection
period
1 bit
D0
D1
True Start
Detection
D2
D3
D4
D5
D6
D7
11011A–ATARM–04-Oct-10
11011A–ATARM–04-Oct-10
Parity Bit
D0
Stop Bit
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