ATMEGA644PA-PU Atmel, ATMEGA644PA-PU Datasheet - Page 163

• Manufacturer Part Number: ATMEGA644PA-PU
• Description: IC MCU 8BIT 64KB FLASH 40DIP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA644PA-PU

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 20MHz
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 64KB (32K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 2K x 8
• Ram Size: 4K x 8
• Voltage - Supply (vcc/vdd): 1.8 V ~ 5.5 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-DIP (0.600", 15.24mm)
• Processor Series: ATMEGA64x
• Core: AVR8
• Data Bus Width: 8 bit
• Data Ram Size: 4 KB
• Interface Type: SPI, TWI, UART
• Maximum Clock Frequency: 20 MHz
• Number Of Programmable I/os: 32
• Operating Supply Voltage: 1.8 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: Through Hole
• 3rd Party Development Tools: EWAVR, EWAVR-BL
• Development Tools By Supplier: ATAVRDRAGON, ATSTK500, ATSTK600, ATAVRISP2, ATAVRONEKIT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

164A/164PA/324A/324PA/644A/644PA/1284/1284P
(1)
Figure 17-1. SPI Block Diagram
DIVIDER
/2/4/8/16/32/64/128
Note:
1. Refer to
Figure 1-1 on page
2, and
Table 13-6 on page 83
for SPI pin placement.
The interconnection between Master and Slave CPUs with SPI is shown in
Figure
17-2. The sys-
tem 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 Mas-
ter 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
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