ATMEGA48V_11 ATMEL [ATMEL Corporation], ATMEGA48V_11 Datasheet - Page 205

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ATMEGA48V_11

Manufacturer Part Number
ATMEGA48V_11
Description
8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash
Manufacturer
ATMEL [ATMEL Corporation]
Datasheet
21.7
2545T–AVR–05/11
AVR USART MSPIM vs. AVR SPI
The USART in MSPIM mode is fully compatible with the AVR SPI regarding:
• Master mode timing diagram
• The UCPOLn bit functionality is identical to the SPI CPOL bit
• The UCPHAn bit functionality is identical to the SPI CPHA bit
• The UDORDn bit functionality is identical to the SPI DORD bit
However, since the USART in MSPIM mode reuses the USART resources, the use of the
USART in MSPIM mode is somewhat different compared to the SPI. In addition to differences of
the control register bits, and that only master operation is supported by the USART in MSPIM
mode, the following features differ between the two modules:
• The USART in MSPIM mode includes (double) buffering of the transmitter. The SPI has no
• The USART in MSPIM mode receiver includes an additional buffer level
• The SPI WCOL (Write Collision) bit is not included in USART in MSPIM mode
• The SPI double speed mode (SPI2X) bit is not included. However, the same effect is achieved
• Interrupt timing is not compatible
• Pin control differs due to the master only operation of the USART in MSPIM mode
A comparison of the USART in MSPIM mode and the SPI pins is shown in
Table 21-3.
buffer
by setting UBRRn accordingly
USART_MSPIM
XCKn
RxDn
TxDn
(N/A)
Comparison of USART in MSPIM mode and SPI pins.
MOSI
MISO
SCK
SPI
SS
ATmega48/88/168
Comment
Master out only
Master in only
(Functionally identical)
Not supported by USART in
MSPIM
Table
21-3.
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