AT90USB1286-16MU ATMEL [ATMEL Corporation], AT90USB1286-16MU Datasheet - Page 209

• Manufacturer Part Number: AT90USB1286-16MU
• Description: Microcontroller with 64/128K Bytes of ISP Flash and USB Controller
• Manufacturer: ATMEL [ATMEL Corporation]

19.4
19.4.1
7593A–AVR–02/06
Frame Formats
USART MSPIM Initialization
ality is summarized in
all ongoing communication for both the Receiver and Transmitter.
Table 19-2.
Figure 19-1. UCPHAn and UCPOLn data transfer timing diagrams.
A serial frame for the MSPIM is defined to be one character of 8 data bits. The USART in MSPIM
mode has two valid frame formats:
A frame starts with the least or most significant data bit. Then the next data bits, up to a total of
eight, are succeeding, ending with the most or least significant bit accordingly. When a complete
frame is transmitted, a new frame can directly follow it, or the communication line can be set to
an idle (high) state.
The UDORDn bit in UCSRnC sets the frame format used by the USART in MSPIM mode. The
Receiver and Transmitter use the same setting. Note that changing the setting of any of these
bits will corrupt all ongoing communication for both the Receiver and Transmitter.
16-bit data transfer can be achieved by writing two data bytes to UDRn. A UART transmit com-
plete interrupt will then signal that the 16-bit value has been shifted out.
The USART in MSPIM mode has to be initialized before any communication can take place. The
initialization process normally consists of setting the baud rate, setting master mode of operation
(by setting DDR_XCKn to one), setting frame format and enabling the Transmitter and the
Receiver. Only the transmitter can operate independently. For interrupt driven USART opera-
• 8-bit data with MSB first
• 8-bit data with LSB first
UCPOLn
0
0
1
1
Data setup (TXD)
Data sample (RXD)
XCK
XCK
Data setup (TXD)
Data sample (RXD)
UCPOLn and UCPHAn Functionality-
UCPHAn
0
1
0
1
Table
UCPOL=0
19-2. Note that changing the setting of any of these bits will corrupt
SPI Mode
0
1
2
3
Leading Edge
Sample (Rising)
Setup (Rising)
Sample (Falling)
Setup (Falling)
Data setup (TXD)
Data setup (TXD)
XCK
Data sample (RXD)
XCK
Data sample (RXD)
AT90USB64/128
Trailing Edge
Setup (Falling)
Sample (Falling)
Setup (Rising)
Sample (Rising)
UCPOL=1
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