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33793
(Rev.:2010)

Distributed System Interface (DSI) Sensor Interface

Freescale Semiconductor 

FUNCTIONAL DEVICE OPERATION

DSI COMMANDS AND RESPONSES

REQUEST VALUE n COMMAND

This command will cause the analog level at one of the

four I/O lines to be measured and returned on the following

command. The command format is found in Table 13. The

analog input measured is defined in Table 14.

Table 13. Request Value n Command Format

Data

Address

Command

CRC

–

–

–

–

–

–

–

– A3 A2 A1 A0 C3 C2 C1 C0 X3 X2 X1 X0

Legend

A[3:0] = Address bits. The address of the selected device.

An address value of "0000" is ignored by all devices.

C[3:0] = Command number.

X[3:0] = Cyclic Redundancy Check (CRC). The CRC as calculated by the

master.

Table 14. Analog Input Selection

Command

A/D Input

0010

I/O0

0101

I/O1

0110

I/O2

1000

I/O3

REQUEST VALUES RESPONSE

This response is an 8-bit value representing the value

measured by the ADC. The selection of “n” is a function of the

command. This is shown in Table 15.

The read will be completed during the idle period and will

represent the voltage at the end of the command. If an

undervoltage condition exists at any time during the

command or the measurement has not completed properly, a

value of “00000000” will be returned. This is a reserved value

to indicate a problem with the measurement. The minimum

valid level reported will be “00000001”. No response is

generated if the command address field was $0.

Table 15. Request Values Response Format

High Byte

Low Byte

CRC

A3 A2 A1 A0 0 0 0 0 D7 D6 D5 D4 D3 D2 D1 D0 X3 X2 X1 X0

Legend

A[3:0] = Address bits. The address of the selected device.

An address value of "0000" is ignored by all devices.

D[7:0] = Measured value (MSB = D7).

X[3:0] = Cyclic Redundancy Check (CRC).

I/O CONTROL COMMAND

This register controls the I/O ports. When the “DR” bits are

set, the corresponding I/O is enabled as an output. The “L” bit

settings control the level of the corresponding I/O if it is

enabled as an output. The format of this command is shown

in Table 16.

Table 16. I/O Control Command Format

Data

Address

Command

CRC

L3 L2 L1 L0 DR3 DR2 DR1 DR0 A3

Legend

A[3:0] = Address bits.

DR[3:0] = I/O direction bits. 1 = Output. All bits are set to “0” by

reset/clear.

A2 A1 A0 0 0 1 1 X3 X2 X1 X0

L[3:0] = Level to output on I/O if configured as output. All bits are set to “0”

by reset/clear

X[3:0] = Cyclic Redundancy Check (CRC). The CRC as calculated by the

master.

I/O CONTROL RESPONSE

The response indicates which I/O has been configured as

outputs and their current values.

The values returned will be the values programmed. The

values at the pins will not be the ones that were programmed

if the pin has been forced to the opposite state. The response

format is shown in Table 17. No response is generated if the

command address field was $0.

Analog Integrated Circuit Device Data

Freescale Semiconductor

33793

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