HT46R01M datasheet(45/69 Pages) HOLTEK

45 / 69 page

HT46R01M/HT46R02M/HT48R01M/HT48R02M

Rev. 1.10

March 8, 2010

Programming Considerations

When programming, special attention must be given to

the PCR[3:0] bits in the register. If these bits are all

cleared to zero no external pins will be selected for use

as A/D input pins allowing the pins to be used as normal

I/O pins. When this happens the internal A/D circuitry

will be power down. Setting the ADONB bit high has the

ability to power down the internal A/D circuitry, which

may be an important consideration in power sensitive

applications.

A/D Transfer Function

As the device contain a 12-bit A/D converter, its

full-scale converted digitised value is equal to FFFH.

Since the full-scale analog input value is equal to the

VDD voltage, this gives a single bit analog input value of

VDD/4096. The diagram show the ideal transfer function

between the analog input value and the digitised output

value for the A/D converter.

Note that to reduce the quantisation error, a 0.5 LSB off-

set is added to the A/D Converter input. Except for the

digitised zero value, the subsequent digitised values will

change at a point 0.5 LSB below where they would

change without the offset, and the last full scale digitised

value will change at a point 1.5 LSB below the VDD level.

A/D Programming Example

The following two programming examples illustrate how

to setup and implement an A/D conversion. In the first

example, the method of polling the EOCB bit in the

ADCR register is used to detect when the conversion

cycle is complete, whereas in the second example, the

A/D interrupt is used to determine when the conversion

is complete.

t A D C

A / D c o n v e r s i o n t i m e

0 0 0 B

x x B

x x x B - P C R [ 3 : 0 ] i s n o t e q u a l t o " 0 "

1 0 B

S T A R T

E O C B

P C R 3 ~

P C R 0

A C S 1 ~

A C S 0

P o w e r - o n

R e s e t

E n d o f A / D

c o n v e r s i o n

1 : D e f i n e p o r t c o n f i g u r a t i o n

2 : S e l e c t a n a l o g c h a n n e l

A / D c l o c k m u s t b e f s y s , f S Y S / 2 , f S Y S / 4 , f S Y S / 8 , f S Y S / 1 6 o r f S Y S / 3 2

t A D C S = 4 t A D

t A D C = 1 6 t A D

N o t e :

S t a r t o f A / D

c o n v e r s i o n

R e s e t A / D

c o n v e r t e r

A / D s a m p l i n g t i m e

t A D C S

0 0 B

S t a r t o f A / D

c o n v e r s i o n

R e s e t A / D

c o n v e r t e r

0 1 B

S t a r t o f A / D

c o n v e r s i o n

R e s e t A / D

c o n v e r t e r

E n d o f A / D

c o n v e r s i o n

A / D s a m p l i n g t i m e

t A D C S

A D C m o d u l e

O N

A D O N B

o f f

o n

t O N 2 S T

t A D C

A / D c o n v e r s i o n t i m e

A/D Conversion Timing

F F E H

(

)

A / D C o n v e r s i o n

R e s u l t

F F F H

F F D H

0 3 H

0 2 H

0 1 H

0 . 5 L S B

4 0 9 3 4 0 9 4 4 0 9 5 4 0 9 6

A n a l o g I n p u t V o l t a g e

1 . 5 L S B

V D D

4 0 9 6

Ideal A/D Transfer Function

HT46R01M Datasheet(PDF) 45 Page - Holtek Semiconductor Inc

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