Datasheet

MC68HC908JL3E Family Data Sheet, Rev. 4
Freescale Semiconductor 97
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
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.
Addr.Register Name Bit 7654321Bit 0
$003C
ADC Status and Control
Register (ADSCR)
Read: COCO
AIEN ADCO ADCH4 ADCH3 ADCH2 ADCH1 ADCH0
Write:
Reset:00011111
$003D
ADC Data Register
(ADR)
Read:AD7AD6AD5AD4AD3AD2AD1AD0
Write:
Reset: Indeterminate after reset
$003E
ADC Input Clock Register
(ADICLK)
Read:
ADIV2 ADIV1 ADIV0
00000
Write:
Reset:00000000
= Unimplemented
Figure 9-1. ADC I/O Register Summary