HT46R064B/065B/066B
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 selection of which analog channel is con-
nected 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 converter end of con-
version status.
The device contains an 4/8-channel analog to digital
converter which can directly interface to external analog
signals, such as that from sensors or other control sig-
nals and convert these signals directly into either a
12-bit digital value.
Input
Conversion
Bits
Input
Pins
Part No.
Channels
HT46R064B
HT46R065B
4
8
12
12
PA0~PA3
The ACS2~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
8 analog inputs must be routed to the converter. It is the
function of the ACS2~ACS0 bits in the ADCR register to
determine which analog channel is actually connected
to the internal A/D converter.
PA0~PA3
PC0~PC1
PC6~PC7
HT46R066B
The accompanying block diagram shows the overall in-
ternal structure of the A/D converter, together with its as-
sociated registers.
The ADCR control register also contains the
PCR2~PCR0 bits which determine which pins on
PA0~PA3, PC0, PC1, PC6, PC7 are used as analog in-
puts for the A/D converter and which pins are to be used
as normal I/O pins. If the 3-bit address on PCR2~PCR0
has a value of ²111², then all eight pins, namely
AN0~AN7 will all be set as analog inputs. Note that if the
PCR2~PCR0 bits are all set to zero, then all the
PA0~PA3, PC0, PC1, PC6, PC7 pins will be setup as nor-
mal I/Os.
A/D Converter Data Registers - ADRL, ADRH
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
53
October 23, 2012
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
