HT46R01B/02B/01N/02N
HT48R01B/02B/01N/02N
Analog to Digital Converter
The need to interface to real world analog signals is a
common requirement for many electronic systems.
However, to properly process these signals by a
microcontroller, they must first be converted into digital
signals by A/D converters. By integrating the A/D con-
version electronic circuitry into the microcontroller, the
need for external components is reduced significantly
with the corresponding follow-on benefits of lower costs
and reduced component space requirements.
In the following table, D0~D11 is the A/D conversion
data result bits.
Bit Bit Bit Bit Bit Bit Bit Bit
Register
7
6
5
4
3
2
1
0
ADRL
D3 D2 D1 D0
¾
¾
¾
¾
ADRH D11 D10 D9 D8 D7 D6 D5 D4
A/D Data Registers
A/D Converter Control Registers - ADCR, ACSR
A/D Overview
To control the function and operation of the A/D con-
verter, two control registers known as ADCR and ACSR
are provided. These 8-bit registers define functions
such as the on/off function, selection of which analog
channel is connected to the internal A/D converter,
which pins are used as analog inputs and which are
used as normal I/Os, the A/D clock source as well as
controlling the start function and monitoring the A/D con-
verter end of conversion status.
The device contains an 4-channel analog to digital con-
verter which can directly interface to external analog sig-
nals, such as that from sensors or other control signals
and convert these signals directly into either a 12-bit dig-
ital value.
The accompanying block diagram shows the overall in-
ternal structure of the A/D converter, together with its as-
sociated registers.
A/D Converter Data Registers - ADRL, ADRH
The ACS1~ACS0 bits in the ADCR register define the
channel number. As the device contains only one actual
analog to digital converter circuit, each of the individual
4 analog inputs must be routed to the converter. It is the
function of the ACS1~ACS0 bits in the ADCR register to
determine which analog channel is actually connected
to the internal A/D converter.
The device, which has an internal 12-bit A/D converter,
requires two data registers, a high byte register, known
as ADRH, and a low byte register, known as ADRL. After
the conversion process takes place, these registers can
be directly read by the microcontroller to obtain the digit-
ised conversion value. Only the high byte register,
ADRH, utilises its full 8-bit contents. The low byte regis-
ter utilises only 4 bit of its 8-bit contents as it contains
only the lowest bits of the 12-bit converted value.
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A/D Converter Structure
Rev.1.10
43
February 12, 2010
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
