ht82a836r Holtek Semiconductor Inc., ht82a836r Datasheet - Page 54

• Manufacturer Part Number: ht82a836r
• Description: Usb Audio Mcu
• Manufacturer: Holtek Semiconductor Inc.

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.
A/D Overview
The device contains a 6-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 a 12-bit digital
value.
The following diagram shows the overall internal struc-
ture of the A/D converter, together with its associated
registers.
A/D Converter Data Registers - ADRL, ADRH
For the HT82A836R device, which has a 12-bit A/D con-
verter, two registers are required, a high byte register,
known as ADRH, and a low byte register, known as
ADRL, to store the 12-bit analog to digital conversion
value. After the conversion process takes place, these
registers can be directly read by the microcontroller to
obtain the digitised conversion value. Note that only the
high byte register ADRH utilises its full 8-bit contents.
The low byte register utilises only 4 bits of its 8-bit con-
tents as it contains only the lowest bit of the 12-bit con-
verted value.
Rev. 1.00
A/D Converter Structure
54
In the following tables, D0~D11 are the A/D conversion
data result bits.
A/D Converter Control Register - ADCR
To control the function and operation of the A/D con-
verter, a control register known as ADCR is provided.
This 8-bit register defines functions such as the selec-
tion of which analog channel is connected to the internal
A/D converter, power on/off the A/D converter, control
the start function and monitoring the A/D converter end
of conversion status.
One section of this register contains the bits
ACS2~ACS0 which define the channel number. As each
of the devices contains only one actual analog to digital
converter circuit, each of the individual 6 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 inter-
nal A/D converter.
The ADCR control register also contains the
PCR2~PCR0 bits which determine power on/off the A/D
converter and. If the PCR2~PCR0 bits are all set to
zero, then the internal A/D converter circuitry will be
powered off to reduce the power consumption. Any
other non-zero combination on the PCR2~PCR0 bits
will power-on the the A/D converter will be power on
which will consume a certain amount of power.
Register Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0
ADRH
ADRL
D11 D10 D9
A/D Converter Data Register
D3
D2
D1
D0
D8
D7
HT82A836R
March 20, 2008
D6
D5
D4