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169 Programmable Hardware Manual (PHM)

The C/D line defines whether the data is exchanged with the configuration register

(C/D is LOW), or data register that contains the conversion result (C/D is HIGH).

The C/D line must remain stable (HIGH or LOW) for the entire duration of the

transaction.

Read and write "transactions" are illustrated on the diagram below.

The A/D converter has 8 inputs and three control lines -- CHS2, CHS1, and CHS0 --

are used to select the channel. Only one channel can be selected at any given

time.

Preparing to communicate with the A/D converter

Before you start exchanging data with the A/D converter you need to configure

certain GPIO lines of the EM1000 as outputs. These lines are CLOCK, DO, C/D, TFS,

RFS, CHS0, CHS1, and CHS2. In other words, all lines except DI must be configured

as outputs.

Writing to the configuration register

Follow these steps to write to the configuration register:

Set the C/D line LOW to indicate that the configuration register access will take

place.

Set the TFS line LOW to indicate that this will be a write operation (RFS must

remain HIGH).

Place the value of the most significant bit of the configuration word on the DO

line.

Set the CLOCK line HIGH.

Set the CLOCK line LOW. This will conclude the first clock pulse.

Tibbo DS1100 User Manual

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