MC33596FCAER2(2007) Просмотр технического описания (PDF) - Freescale Semiconductor

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производитель

MC33596FCAER2
(Rev.:2007)

PLL Tuned UHF Receiver for Data Transfer Applications

Freescale Semiconductor 

Communication Protocol

• If strobe pin is 0 the state is OFF.

• If strobe pin is released from 0 while state is OFF, the initial OFF period is completed.

• Whenever is the change of duration of one state due to STROBE pin level or a message being

received, this has no influence on the timing of the following states (A, B, or OFF).

10.4 Standby: LVD Mode

The SPI is deselected. Nothing is sent and all incoming data are ignored until CONFB and SEB go low to

switch back to configuration mode.

11 Communication Protocol

11.1 Manchester Coding Description

The MC33596 data manager is able to decode Manchester coded messages. For other codings, the data

manager should be disabled (DME=0) for RAW data to be available on MOSI.

Manchester coding is defined as follows: data is sent during the first half-bit; and the complement of the

data is sent during the second half-bit.

0

1

0

0

1

1

0

ORIGINAL

DATA

MANCHESTER

CODED DATA

Figure 7. Example of Manchester Coding

The signal average value is constant. This allows clock recovery from the data stream itself. To achieve

correct clock recovery, Manchester coded data must have a duty cycle between 47% and 53%.

11.2 Preamble, Identifier, Header, and Message

The following description applies if the data manager is enabled (DME = 1).

A complete telegram includes the following sequences: a preamble, an identifier (ID), the preamble again,

a header, the message, and an end-of-message (EOM). These bit sequences are described below.

• Preamble: A preamble is required before the ID and before the header. It enables:

— In the case of OOK modulation, the AGC to settle, and the data slicer reference voltage to

settle if DSREF = 1

— In the case of FSK modulation, the data slicer reference voltage to settle

— Clock recovery

The preamble content must be defined carefully, to ensure that it will not be decoded as the ID or

the header. Figure 8 defines the preamble in OOK and FSK modulation.

MC33596 Data Sheet, Rev. 3

18

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