HT46R068B/HT46R069B
Enhanced A/D Type 8-bit OTP MCU
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 , they must first be converted into digital
signals by A/D converters. By integrating the A/D conversion electronic circuitry into the , 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 an 4/8-channel analog to digital converter which can directly interface to
external analog signals, such as that from sensors or other control signals and convert these signals
directly into either a 12-bit digital value.
Part No.
Input Channels
Conversion Bits
Input Pins
PA0~PA3
PC0~PC1
PCꢄ~PC7
PE0~PE7
HT4ꢄR0ꢄ8B
1ꢄ
1ꢃ
HT4ꢄR0ꢄ9B
The accompanying block diagram shows the overall internal structure of the A/D converter,
together with its associated registers.
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 digitised
conversion value. Only the high byte register, ADRH, utilises its full 8-bit contents. The low
byte register utilises only 4 bit of its 8-bit contents as it contains only the lowest bits of the 12-bit
converted value.
In the following table, D0~D11 is the A/D conversion data result bits.
Register
ADRL
Bit7
D3
Bit6
Dꢃ
Bit5
D1
Bit4
D0
Bit3
—
Bit2
—
Bit1
—
Bit0
—
ADRH
D4
D11
D10
D9
D8
D7
Dꢄ
D5
A/D Data Registers
A/D Converter Control Registers – ADCR, ACSR, ANCSR1, ANCSR0
To control the function and operation of the A/D converter, four control registers known as ADCR,
ACSR, ANCSR1 and ANCSR0 are provided. These 8-bit registers define functions such as the
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 converter end of conversion status.
The ACS3~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 ACS3~ACS0 bits in the ADCR register to
determine which analog channel is actually connected to the internal A/D converter.
The two control registers, ANCSR1,ANCSR0, determine which pins on PA0~PA3, PC0, PC1,
PC6, PC7, PE0~PE7 are used as analog inputs for the A/D converter and which pins are to be
used as normal I/O pins. If the 16-bit address on PCR15~PCR0 has a value of “FFH”, then all 16
pins, namely AN0~AN15 will all be set as analog inputs. To reduce the power consumption in
Rev. 1.00
ꢄ1
�anꢀaꢁꢂ ꢃꢄꢅ ꢃ011
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
