7721 datasheet(255/577 Pages) RENESAS

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A-D CONVERTER

7721 Group User’s Manual

12–4

12.2.1 A-D control register

Figure 12.2.2 shows the structure of the A-D control register. The A-D operation mode select bit selects

the operation mode of the A-D converter. The other bits are described below.

12.2 Block description

Fig. 12.2.2 Structure of A-D control register

(1)

Analog input select bits (bits 2 to 0)

These bits are used to select an analog input pin in the one-shot mode and repeat mode. Pins which

are not selected as analog input pins function as programmable I/O ports.

These bits must be set again when the user switches the A-D operation mode to the one-shot mode

or repeat mode after A-D conversion is performed in the single sweep mode or repeat sweep mode.

A-D control register (Address 1E16)

Bit

A-D conversion frequency

( AD) select bit

A-D conversion start bit

Trigger select bit

A-D operation mode select bits

Bit name

At reset

Undefined

Functions

0 0 0 : AN0 selected

0 0 1 : AN1 selected

0 1 0 : AN2 selected

0 1 1 : AN3 selected

1 0 0 : AN4 selected

1 0 1 : AN5 selected

1 1 0 : AN6 selected

1 1 1 : AN7 selected (Note 2)

b2 b1 b0

0 : Internal trigger

1 : External trigger

0 0 : One-shot mode

0 1 : Repeat mode

1 0 : Single sweep mode

1 1 : Repeat sweep mode

0 : Stop A-D conversion

1 : Start A-D conversion

b4 b3

Notes 1: These bits are ignored in the single sweep and repeat sweep mode. (They may be

either “0” or “1.”)

2: When an external trigger is selected, the AN7 pin cannot be used as an analog input

pin.

3: Writing to each bit (except bit 6) of the A-D control register must be performed while

the A-D converter halts.

Analog input select bits

(Valid in one-shot and repeat

modes) (Note 1)

Undefined

0 : f2 divided by 4

1 : f2 divided by 2

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