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AN1816

USING THE HC912B32 TO IMPLEMENT THE DISTRIBUTED SYSTEMS INTERFACE (DSI) PROTOCOL

Freescale Semiconductor 

Freescale Semiconductor, Inc.

Distributed Systems Interface (DSI) Overview

Command and

The long word command and control message encoding is shown in

Control Messages Figure 4 Long Word Command and Control Message.

DATA

ADDRESS

COMMAND

CRC

D7 D6 D5 D4 D3 D2 D1 D0 A3 A2 A1 A0 C3 C2 C1 C0 X3 X2 X1 X0

Figure 4 Long Word Command and Control Message

The message consists of 8 bits of data, the encoded 4-bit address of the

intended slave device, a 4-bit encoded command, and the calculated

4-bit CRC.

The short word command and control message encoding is shown in

Figure 5 Short Word Command and Control Message.

Response

Messages

ADDRESS

COMMAND

CRC

A3 A2 A1 A0 C3 C2 C1 C0 X3 X2 X1 X0

Figure 5 Short Word Command and Control Message

The message consists of the encoded 4-bit address of the intended

slave device, a 4-bit encoded command, and the calculated 4-bit CRC.

A long word response message is sent from the slave to the master in

response to a long word command and control message to the slave’s

address. The response is transmitted during the next command and

control message. The long word response message encoding is shown

in Figure 6 Long Word Response Message.

DATA BYTE 1

DATA BYTE 2

CRC

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 X3 X2 X1 X0

Figure 6 Long Word Response Message

The message consists of two 8-bit data bytes and the calculated 4-bit

CRC

A short word response message is sent from the slave to the master in

response to a short word command and control message to the slave’s

address. The response is transmitted during the next command and

AN1816

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