Analog To Digital Converter - Holtek HT66F488 Manual

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 conversion 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 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 a 12-bit digital value.
The accompanying block diagram shows the overall internal structure of the A/D converter, together
with its associated registers.
A C E 7 ~ A C E 0
P B 6 / A N 0 ~ P B 7 / A N 1
P C 3 / A N 3 ~ P C 6 / A N 6
P C 0 / A N 2
P B 1 / A N 7
V 1 2 5 E N
A/D Converter Register Description
Overall operation of the A/D converter is controlled using five registers. A read only register pair
exists to store the ADC data 12-bit value. The remaining three registers are control registers which
setup the operating and control function of the A/D converter.
Register
Name
ADRL(ADRFS=�)
ADRH(ADRFS=�)
ADRL(ADRFS=1)
ADRH(ADRFS=1)
ADCR�
ADCR1
ACERL
Rev. 1.21
A D C K 2 ~ A D C K 0
A / D C l o c k
V
B G
A C S 4 S T A R T
A C S 2 ~ A C S 0
A/D Converter Structure
7 6 5
D3 D2 D1
D11 D1� D�
D� D6 D5
— — —
START EOCB ADOFF
ACS4 V125E� —
ACE� ACE6 ACE5
A/D Converter Register List
1�4
HT66F488/HT66F489
A/D Flash MCU with EEPROM
V
D D
f
S Y S
¸ 2 N
P C 6 / V R E F
( N = 0 ~ 6 )
A D O F F
B i t
V R E F S
B i t
A / D R e f e r e n c e V o l t a g e
A D R L
A / D C o n v e r t e r
A D R H
V
S S
A D R F S
E O C B A D O F F
Bit
4 3 2
D� — —
D8 D� D6
D4 D3 D2
— D11 D1�
ADRFS — ACS2
VREFS1 VREFS� ADCK2
ACE4 ACE3 ACE2
�ove��e� ��� 2�1�
A / D D a t a
R e g i s t e r s
b i t
1 0
— —
D5 D4
D1 D�
D� D8
ACS1 ACS�
ADCK1 ADCK�
ACE1 ACE�