GMS81C2012 datasheet(63/92 Pages) HYNIX

63 / 92 page

Hyundai Micro Electronics

GMS81C2020/GMS81C2120

Nov. 1999 Ver 0.0

preliminary

18. ANALOG TO DIGITAL CONVERTER

The analog-to-digital converter (A/D) allows conversion

of an analog input signal to a corresponding 8-bit digital

value. The A/D module has twelve analog inputs, which

are multiplexed into one sample and hold. The output of

the sample and hold is the input into the converter, which

generates the result via successive approximation.

The A/D module has two registers which are the control

ADCM register, shown in Figure 18-2 , controls the oper-

ation of the A/D converter module. The port pins can be

configured as analog inputs or digital I/O.

To use analog inputs, each port is assigned analog input

port by setting the bit ANSEL[7:0] in R6FUNC register.

Also it is assigned analog input port by setting the bit AN-

SEL[11:8] in R7FUNC register. And selected the corre-

sponding channel to be converted by setting ADS[3:0].

The processing of conversion is start when the start bit

ADST is set to "1". After one cycle, it is cleared by hard-

ware. The register ADCR contains the results of the A/D

conversion. When the conversion is completed, the result

is loaded into the ADCR, the A/D conversion status bit

ADSF is set to "1", and the A/D interrupt flag ADIF is set.

The block diagram of the A/D module is shown in Figure

18-1 . The A/D status bit ADSF is set automatically when

A/D conversion is completed, cleared when A/D conver-

sion is in process. The conversion time takes maximum 20

uS (at fXI=4 MHz).

Figure 18-1 A/D Converter Block Diagram

R67/AN7

ANSEL7

0111

AVDD

ADEN

S/H

Successive

Approximation

Circuit

A D IF

Resistor

Ladder

Circuit

ADS[3:0]

ADCR(8-bit)

Sample & Hold

A/D Interrupt

ADDRESS : EBH

RESET VALUE : Undefined

A/D Result Register

R7FUNC[3:0]

R6FUNC[7:0]

R66/AN6

ANSEL6

0110

R65/AN5

ANSEL5

0101

R64/AN4

ANSEL4

0100

R63/AN3

ANSEL3

0011

R62/AN2

ANSEL2

0010

R61/AN1

ANSEL1

0001

R60/AN0

ANSEL0

0000

R73/AN11

ANSEL11

1011

R72/AN10

ANSEL10

1010

R71/AN9

ANSEL9

1001

R70/AN8

ANSEL8

1000

[ADCM.6]

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