MC908JL3ECPE Datasheet, PDF (97/180 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 9
Analog-to-Digital Converter (ADC)
9.1 Introduction
This section describes the 12-channel, 8-bit linear successive approximation analog-to-digital converter
(ADC).
9.2 Features
Features of the ADC module include:
• 12 channels with multiplexed input
• Linear successive approximation with monotonicity
• 8-bit resolution
• Single or continuous conversion
• Conversion complete flag or conversion complete interrupt
• Selectable ADC clock
Addr.
$003C
$003D
$003E
Register Name
Read:
ADC Status and Control
Register (ADSCR)
Write:
Reset:
Read:
ADC Data Register
(ADR)
Write:
Reset:
Read:
ADC Input Clock Register
(ADICLK)
Write:
Reset:
Bit 7
COCO
0
AD7
ADIV2
0
6
5
AIEN
ADCO
0
0
AD6
AD5
ADIV1 ADIV0
0
0
= Unimplemented
4
ADCH4
1
AD4
3
ADCH3
1
AD3
Indeterminate after reset
0
0
0
0
2
ADCH2
1
AD2
0
0
1
ADCH1
1
AD1
0
0
Bit 0
ADCH0
1
AD0
0
0
Figure 9-1. ADC I/O Register Summary
9.3 Functional Description
Twelve ADC channels are available for sampling external sources at pins PTB0–PTB7 and PTD0–PTD3.
An analog multiplexer allows the single ADC converter to select one of the 12 ADC channels as ADC
voltage input (ADCVIN). ADCVIN is converted by the successive approximation register-based counters.
The ADC resolution is 8 bits. When the conversion is completed, ADC puts the result in the ADC data
register and sets a flag or generates an interrupt. Figure 9-2 shows a block diagram of the ADC.
MC68HC908JL3E Family Data Sheet, Rev. 4
Freescale Semiconductor
97