at91cap7e ATMEL Corporation, at91cap7e Datasheet - Page 354

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

Figure 29-8. NRZ to Manchester Encoding
Figure 29-9. Preamble Patterns, Default Polarity Assumed
354
AT91CAP7E
Manchester
Manchester
Manchester
Manchester
encoded
encoded
encoded
encoded
data
data
data
data
Manchester
sists of a user-defined pattern that indicates the beginning of a valid data.
illustrates these patterns. If the start frame delimiter, also known as start bit, is one bit, (ONEBIT
at 1), a logic zero is Manchester encoded and indicates that a new character is being sent seri-
ally on the line. If the start frame delimiter is a synchronization pattern also referred to as sync
(ONEBIT at 0), a sequence of 3 bit times is sent serially on the line to indicate the start of a new
character. The sync waveform is in itself an invalid Manchester waveform as the transition
The Manchester encoded character can also be encapsulated by adding both a configurable
preamble and a start frame delimiter pattern. Depending on the configuration, the preamble is a
training sequence, composed of a pre-defined pattern with a programmable length from 1 to 15
bit times. If the preamble length is set to 0, the preamble waveform is not generated prior to any
character. The preamble pattern is chosen among the following sequences: ALL_ONE,
ALL_ZERO, ONE_ZERO or ZERO_ONE, writing the field TX_PP in the US_MAN register, the
field TX_PL is used to configure the preamble length.
valid patterns. To improve flexibility, the encoding scheme can be configured using the
TX_MPOL field in the US_MAN register. If the TX_MPOL field is set to zero (default), a logic
zero is encoded with a zero-to-one transition and a logic one is encoded with a one-to-zero tran-
sition. If the TX_MPOL field is set to one, a logic one is encoded with a one-to-zero transition
and a logic zero is encoded with a zero-to-one transition.
A start frame delimiter is to be configured using the ONEBIT field in the US_MR register. It con-
encoded
encoded
NRZ
data
data
Txd
Txd
Txd
Txd
Txd
8 bit width "ZERO_ONE" Preamble
8 bit width "ONE_ZERO" Preamble
8 bit width "ALL_ZERO" Preamble
8 bit width "ALL_ONE" Preamble
1
0
1
1
0
0
Figure 29-9
0
SFD
SFD
SFD
SFD
1
illustrates and defines the
DATA
DATA
DATA
DATA
Figure 29-10
8549A–CAP–10/08