32186 datasheet(536/1032 Pages) RENESAS

536 / 1032 page

A/D CONVERTER

11-38

32185/32186 Group Hardware Manual

Rev.1.10 REJ09B0235-0110 May 15, 07

11.3 Functional Description of A/D Converter

11.3.4 Calculating A/D Conversion Time

The A/D conversion time is expressed by the sum of dummy cycle time and actual execution cycle time.

The following shows each time factor necessary to calculate the conversion time.

1. Start dummy time

A time from when the CPU executed the A/D conversion start instruction to when the A/D

Converter starts A/D conversion

2. A/D conversion execution cycle time

If sample-and-hold is enabled, the sampling time is included in this execution cycle time.

3. Comparate execution cycle time

4. End dummy time

A time from when the A/D Converter has finished A/D conversion to when the CPU can stably

read out the conversion result from the A/D data register.

5. Scan to scan dummy time

A time during single-shot or continuous scan mode from when the A/D Converter has finished

A/D conversion on a channel to when it starts A/D conversion on the next channel.

The equation to calculate the A/D conversion time is as follows:

A/D conversion time = Start dummy time + Execution cycle time

(+ Scan to scan dummy time + Execution cycle time

+ Scan to scan dummy time + Execution cycle time

+ Scan to scan dummy time .... + Execution cycle time)

+ End dummy time

Note: • Enclosed in ( ) are the conversion time required for the second and subsequent

channels to be converted in scan mode.

(1) Calculating the conversion time during A/D conversion mode

The following schematically shows the method for calculating the conversion time during A/D conversion mode.

Start dummy

Execution cycle

A/D conversion

start trigger

Convert operation

starts

Transferred to the

A/D data register

End dummy

Start dummy

Execution cycle

Completed

Execution cycle

End dummy

Scan to

scan dummy

Scan to

scan dummy

(Channel 0)

(Channel 1)

(Last channel)

Figure 11.3.3 Conceptual Diagram of A/D Conversion Time

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