ATmega168A Atmel Corporation, ATmega168A Datasheet - Page 169

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ATmega168A

Manufacturer Part Number
ATmega168A
Description
Manufacturer
Atmel Corporation
Datasheets

Specifications of ATmega168A

Flash (kbytes)
16 Kbytes
Pin Count
32
Max. Operating Frequency
20 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
23
Ext Interrupts
24
Usb Speed
No
Usb Interface
No
Spi
2
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
Yes
Crypto Engine
No
Sram (kbytes)
1
Eeprom (bytes)
512
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 to 5.5
Operating Voltage (vcc)
1.8 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
3
Output Compare Channels
6
Input Capture Channels
1
Pwm Channels
6
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes

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ATmega48A/PA/88A/PA/168A/PA/328/P
(1)
Figure 19-1. SPI Block Diagram
DIVIDER
/2/4/8/16/32/64/128
Note:
1. Refer to
Figure 1-1 on page
2, and
Table 14-3 on page 84
for SPI pin placement.
The interconnection between Master and Slave CPUs with SPI is shown in
Figure 19-2 on page
170. The system consists of two shift Registers, and a Master clock generator. The SPI Master
initiates the communication cycle when pulling low the Slave Select SS pin of the desired Slave.
Master and Slave prepare the data to be sent in their respective shift Registers, and the Master
generates the required clock pulses on the SCK line to interchange data. Data is always shifted
from Master to Slave on the Master Out – Slave In, MOSI, line, and from Slave to Master on the
Master In – Slave Out, MISO, line. After each data packet, the Master will synchronize the Slave
by pulling high the Slave Select, SS, line.
When configured as a Master, the SPI interface has no automatic control of the SS line. This
must be handled by user software before communication can start. When this is done, writing a
byte to the SPI Data Register starts the SPI clock generator, and the hardware shifts the eight
bits into the Slave. After shifting one byte, the SPI clock generator stops, setting the end of
Transmission Flag (SPIF). If the SPI Interrupt Enable bit (SPIE) in the SPCR Register is set, an
interrupt is requested. The Master may continue to shift the next byte by writing it into SPDR, or
signal the end of packet by pulling high the Slave Select, SS line. The last incoming byte will be
kept in the Buffer Register for later use.
When configured as a Slave, the SPI interface will remain sleeping with MISO tri-stated as long
as the SS pin is driven high. In this state, software may update the contents of the SPI Data
Register, SPDR, but the data will not be shifted out by incoming clock pulses on the SCK pin
until the SS pin is driven low. As one byte has been completely shifted, the end of Transmission
Flag, SPIF is set. If the SPI Interrupt Enable bit, SPIE, in the SPCR Register is set, an interrupt
169
8271D–AVR–05/11

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