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AS3977

Data Sheet - A p p l i c a t i o n I n f o r m a t i o n

9.5 Communication and Command Byte Structure

A frame consists of a command byte including address/configuration and a following bit stream that can either represent an integer number of

bytes or a random sequence of bits when the command is transmit. Command is encoded in the 2 first bits, while address is given on 6 bits. In

case if the command is neither read nor write, these bits are used to configure the transmission and they will be stored until the next

configuration.

The first byte of every SDI sequence is the command byte.

The function code defines the command to be performed.

Function Code

Register Address or Transmission Configuration

C0

C1

A5

A4

A3

A2

A1

A0

C0

C1

Command

0

0

Write data to register at address <A5…A0>

0

1

Read data from register at address <A5…A0>

1

0

Not defined

1

1

Transmit data. A0…A5 defines the transmit configuration:

Bit

Function

Value, Description

<A1, A0>

Frequency

Selection

0 (00): selects frequency setting 1

1 (00): selects frequency setting 2

2 (10): selects frequency setting 3

3 (11): selects frequency setting 4

A2

Power level /

modulation type

selection

0: selects power level / modulation type 1

1: selects power level / modulation type 2

A3

Manchester coding

0: off

1: on

A4

PA mode

0: PA off at the falling edge of ENABLE (synchronized

with baud rate if A5 high)

1: DATAIO is latched at the falling edge of ENABLE

(i.e. TX data are kept constant, PA stays on)

A5

Data

Synchronization

0: off

1: on