at91cap7e ATMEL Corporation, at91cap7e Datasheet - Page 353

• Manufacturer Part Number: at91cap7e
• Description: Customizable Microcontroller
• Manufacturer: ATMEL Corporation

Figure 29-6. Character Transmit
Figure 29-7. Transmitter Status
29.6.3.2
8549A–CAP–10/08
Manchester Encoder
Baud Rate
TXEMPTY
Baud Rate
Example: 8-bit, Parity Enabled One Stop
US_THR
TXRDY
Clock
Write
Clock
TXD
TXD
encoded based on biphase Manchester II format. To enable this mode, set the MAN field in the
US_MR register to 1. Depending on polarity configuration, a logic level (zero or one), is transmit-
ted as a coded signal one-to-zero or zero-to-one. Thus, a transition always occurs at the
When the Manchester encoder is in use, characters transmitted through the USART are
The characters are sent by writing in the Transmit Holding Register (US_THR). The transmitter
reports two status bits in the Channel Status Register (US_CSR): TXRDY (Transmitter Ready),
which indicates that US_THR is empty and TXEMPTY, which indicates that all the characters
written in US_THR have been processed. When the current character processing is completed,
the last character written in US_THR is transferred into the Shift Register of the transmitter and
US_THR becomes empty, thus TXRDY raises.
Both TXRDY and TXEMPTY bits are low since the transmitter is disabled. Writing a character in
US_THR while TXRDY is active has no effect and the written character is lost.
midpoint of each bit time. It consumes more bandwidth than the original NRZ signal (2x) but the
receiver has more error control since the expected input must show a change at the center of a
bit cell. An example of Manchester encoded sequence is: the byte 0xB1 or 10110001 encodes
to 10 01 10 10 01 01 01 10, assuming the default polarity of the encoder.
this coding scheme.
Start
Bit
Start
Bit
D0
D1
D0
D2
D3
D1
D4
D5
D2
D6
D7
D3
Parity
Bit
Stop
Bit
D4
Start
Bit
D0
D5
D1
D2
D6
D3
D4
D7
D5
D6
Parity
Bit
D7
Parity
Bit
Stop
Bit
AT91CAP7E
Stop
Bit
Figure 29-8
illustrates
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