AT90PWM2 datasheet(214/365 Pages) ATMEL

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4317K–AVR–03/2013

AT90PWM2/3/2B/3B

19.3.3

Manchester encoding

Manchester encoding (also know as Biphase Code) is a synchronous clock encoding technique

used to encode the clock and data of a synchronous bit stream. In this technique, the actual

binary data to be transmitted are not sent as a sequence of logic 1's and 0's as in level encoded

way as in standard USART (known technically as Non Return to Zero (NRZ)). Instead, the bits

are translated into a slightly different format that has a number of advantages over using straight

binary encoding (i.e. NRZ).

Manchester encoding follows the rules:

•

If the original data is a Logic 1, the Manchester code is: 0 to 1 (upward transition at bit

center)

•

If the original data is a Logic 0, the Manchester code is: 1 to 0 (downward transition at bit

center)

Figure 19-2. Manchester Bi-phase levels

19.3.3.1

Manchester frame

The USART supports Manchester encoded frames with the following characteristics:

•

One start bit Manchester encoded (logical ‘1’)

•

5, 6, 7, 8, 9, 13, 14,15,16,17 data bits in transmission or reception (MSB or LSB first)

•

The number of data bit in a frame is independently configurable in reception and

transmission mode.

•

One or Two stop bits (level encoded)

Figure 19-3. Manchester Frame example

Logical 0

Logical 1

Start

Bit

Data Bits

(up to 17 data bit)

Stop

Bits

Encoder Clock

Manchester Data

Binary Data

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