TMP93CS41 datasheet(202/248 Pages) TOSHIBA

202 / 248 page

TMP93CS40/TMP93CS41

2004-02-10

93CS40-200

3.12.1

Operation

(1) Analog reference voltage

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

reference voltage is applied to the VREFL pin.

The reference voltage between VREFH and VREFL is divided by 1024 (using string

resistance) and compared with the analog input voltage for AD conversion.

The switch between VREFH and VREFL can be turned off by writing “0” to

ADMOD2<VREFON>.

When <VRFFON>

= “0”, before the conversion can start, must be written to

<VREFON> and a 3

µs period must be allowed so that the internal reference voltage

can stabilize (regardless of fc) before “1” is written to ADMOD1<ADS>.

(2) Analog input channels

The analog input channel is selected by ADMOD2<ADCH2:0>. However, the channel

which should be selected depends on the operation mode of the AD converter.

In fixed analog input mode, one channel is selected out of eight pins, AN0 to AN7, by

<ADCH2:0>.

In analog input channel scan mode, the number of channels to be scanned is

specified by ADMOD2<ADCH2:0>. For example, AN0 only, AN0

→ AN1, AN0 → AN1

→ AN2, AN0 → AN1 → AN2 → AN3, AN4 only, AN4 → AN5, AN4 → AN5 → AN6, or

AN4

→ AN5 → AN6 → AN7.

When reset the AD conversion channel register will be initialized to

ADMOD2<ADCH2:0>

= “000”, so that the AN0 pin is selected.

The pins which are not used as analog input channels can be used as ordinary input

port pins for port P5.

(3) Starting AD conversion

AD conversion starts when “1” is written to the AD conversion register

ADMOD1<ADS>. When conversion starts, the conversion busy flag ADMOD1<ADBF>,

which indicates that conversion is in progress, is set to “1”.

(4) AD conversion mode

Both fixed AD conversion channel mode and conversion channel scan mode include

two conversion modes; single and repeat conversion mode.

In fixed channel repeat mode, conversion of the specified single channel is executed

repeatedly.

In scan repeat mode, scanning is executed repeatedly.

The AD conversion mode is selected by ADMOD1<REPET, SCAN>.

(5) AD conversion speed selection

There are four AD conversion speed modes. The selection is made by the

ADMOD2<SPEED1:0> register.

When reset, <SPEED1:0> is initialized to “00”, selecting 160-state conversion mode

(16

µs at 20 MHz).

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