ATMEGA328P-20PU Atmel, ATMEGA328P-20PU Datasheet - Page 201

• Manufacturer Part Number: ATMEGA328P-20PU
• Manufacturer: Atmel

Specifications of ATMEGA328P-20PU

• Cpu Family: ATmega
• Device Core: AVR
• Device Core Size: 8b
• Frequency (max): 20MHz
• Interface Type: SPI/TWI/USART
• Program Memory Type: Flash
• Program Memory Size: 32KB
• Total Internal Ram Size: 2KB
• # I/os (max): 23
• Number Of Timers - General Purpose: 3
• Operating Supply Voltage (typ): 3.3/5V
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 2.7V
• On-chip Adc: 6-chx10-bit
• Instruction Set Architecture: RISC
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Through Hole
• Pin Count: 28
• Package Type: PDIP
• Lead Free Status / Rohs Status: Compliant

20. USART in SPI Mode
20.1
20.2
20.3
8025K–AVR–10/09
Features
Overview
Clock Generation
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The Universal Synchronous and Asynchronous serial Receiver and Transmitter (USART) can be
set to a master SPI compliant mode of operation.
Setting both UMSELn1:0 bits to one enables the USART in MSPIM logic. In this mode of opera-
tion the SPI master control logic takes direct control over the USART resources. These
resources include the transmitter and receiver shift register and buffers, and the baud rate gen-
erator. The parity generator and checker, the data and clock recovery logic, and the RX and TX
control logic is disabled. The USART RX and TX control logic is replaced by a common SPI
transfer control logic. However, the pin control logic and interrupt generation logic is identical in
both modes of operation.
The I/O register locations are the same in both modes. However, some of the functionality of the
control registers changes when using MSPIM.
The Clock Generation logic generates the base clock for the Transmitter and Receiver. For
USART MSPIM mode of operation only internal clock generation (i.e. master operation) is sup-
ported. The Data Direction Register for the XCKn pin (DDR_XCKn) must therefore be set to one
(i.e. as output) for the USART in MSPIM to operate correctly. Preferably the DDR_XCKn should
be set up before the USART in MSPIM is enabled (i.e. TXENn and RXENn bit set to one).
The internal clock generation used in MSPIM mode is identical to the USART synchronous mas-
ter mode. The baud rate or UBRRn setting can therefore be calculated using the same
equations, see
Full Duplex, Three-wire Synchronous Data Transfer
Master Operation
Supports all four SPI Modes of Operation (Mode 0, 1, 2, and 3)
LSB First or MSB First Data Transfer (Configurable Data Order)
Queued Operation (Double Buffered)
High Resolution Baud Rate Generator
High Speed Operation (fXCKmax = f
Flexible Interrupt Generation
Table
20-1:
CK
/2)
ATmega48P/88P/168P
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