Hyundai Micro Electronics
GMS81C2020/GMS81C2120
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.
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).
The A/D module has two registers which are the control
register ADCM and A/D result register ADCR. The
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-
ADS[3:0]
R6FUNC[7:0]
R7FUNC[3:0]
1011
1010
0111
R73/AN11
R67/AN7
ANSEL11
R72/AN10
ANSEL7
0110
0101
0100
0011
0010
R66/AN6
R65/AN5
R64/AN4
R63/AN3
R62/AN2
ANSEL10
ANSEL6
ANSEL5
ANSEL4
ANSEL3
ANSEL2
1001
1000
R71/AN9
ANSEL9
R70/AN8
ANSEL8
A/D Result Register
ADDRESS : EBH
ADCR(8-bit)
RESET VALUE : Undefined
0001
0000
R61/AN1
R60/AN0
Sample & Hold
S/H
ANSEL1
ANSEL0
COMPARATOR
Successive
Approximation
Circuit
ADIF
A/D Interrupt
Resistor
Ladder
Circuit
AVDD
ADEN
[ADCM.6]
Figure 18-1 A/D Converter Block Diagram
Nov. 1999 Ver 0.0
preliminary
63
HYNIX [ HYNIX SEMICONDUCTOR ]
