HMS81C2012A Datasheet, PDF (63/107 Pages) List of Unclassifed Manufacturers – CMOS Single-Chip 8-Bit Microcontroller with A/D Converter & VFD Driver

HMS81C2012A/2020A
13. ANALOG 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 eight analog inputs, which are
multiplexed into one sample and hold. The output of the
sample and hold is the input into the converter, which gen-
erates the result via successive approximation. The analog
supply voltage is connected to AV_DD of ladder resistance
of A/D module.
The A/D module has two registers which are the control
register ADCM and A/D result register ADR. The register
ADCM, shown in Figure 13-1, controls the operation 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].
How to Use A/D Converter
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
13-2. 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)
ADCM
ADCR
R/W R/W R/W R/W R/W R
7
6
5
4
3
2
1
0
- _{ADEN ADS3 ADS2} BATDCSL1 _{ADS0 ADST ADSF}
ADDRESS: 0EA_H
INITIAL VALUE: -000 0001_B
A/D status bit
0: A/D conversion is in progress
1: A/D conversion is completed
A/D start bit
Setting this bit starts an A/D conversion.
After one cycle, bit is cleared to “0” by hardware.
Analog input channel select
0000: Channel 0 (AN0)
0001: Channel 1 (AN1)
0010: Channel 2 (AN2)
0011: Channel 3 (AN3)
0100: Channel 4 (AN4)
0101: Channel 5 (AN5)
0110: Channel 6 (AN6)
0111: Channel 7 (AN7)
1000: Channel 8 (AN8)
1001: Channel 9 (AN9)
1010: Channel 10 (AN10)
1011: Channel 11 (AN11)
A/D converter Enable bit
0: A/D converter module turn off and
current is not flow.
1: Enable A/D converter
R R R R RR R R
76543210
BTCL
A/D Conversion Data
ADDRESS: 0EB_H
INITIAL VALUE: Undefined
Figure 13-1 A/D Converter Control Register
SEP. 2004 Ver 2.00
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