TMP93CS32F datasheet(140/180 Pages) TOSHIBA

140 / 180 page

TMP93CS32

2004-02-10

93CS32-138

3.10.2

Operation

(1) Analog reference voltage

High analog reference voltage is applied to the VREFH pin, and low analog reference

voltage is applied to the VREFL pin. The voltage between VREFH and VREFL is

divided into 1024 increments using a string resistor. AD conversion is based on

comparing the analog input voltage with these reference voltage increments.

To turn the switch between VREFH and VREFL off, program “0” to the

ADMOD1<VREFON> bit.

To start AD conversion when the switch is off, first program “1” to <VREFON>. After

that, wait at 3

µs long enough to get the stabilized oscillation, program “1” to

ADMOD0<ADS>.

(2) Selecting analog input channels

The procedure for selecting analog input channels depends on the operating mode of

the AD converter.

•

When analog input channel is used to fix (ADMOD0<SCAN>

= “0”)

To set ADMOD1<ADCH2:0>, selecting one channel from analog input pins AN0

to AN5.

•

When analog input channel is used to scan (ADMOD0<SCAN>

= “1”)

To set ADMOD1<ADCH2:0>, selecting one channel from 6 scan mode.

Table 3.10.1 shows the analog input channel selection each operating mode.

A reset initializes AD mode control register ADMOD1<ADCH2:0> to “000”,

selecting pin AN0 for the AD converter input.

The pins not used as analog input channels can be used as general-purpose input

ports (P5).

Table 3.10.1 Analog Input Channel Selection

<ADCH2:0>

Fixed Channel

<SCAN>

= 0

Channel Scan

<SCAN>

= 1

000

AN0

001

AN1

AN0

→ AN1

010

AN2

AN0

→ AN1 → AN2

011

AN3

AN0

→ AN1 → AN2 → AN3

100

AN4

101

AN5

AN4

→ AN5

110

111

Don’t care

(3) Starting AD conversion

AD conversion starts when ADMOD0<ADS> to “1”, or ADMOD1<ADTRGE> is set to

“1” and the falling edge is input through ADTRG pin.

When AD conversion starts, AD conversion busy flag ADMOD0<ADBF> is set to “1”,

indicating AD conversion is in progress.

Writing “1” to <ADS> while conversion is in progress restarts the conversion. Check

the conversion result stored flag ADREGxL<ADRxRF> to determine whether the AD

conversion data are valid at this time.

Inputting the falling edge to the ADTRG pin while conversion is in progress is

invalid.

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