MC68HC908GR8 Datasheet, PDF (58/286 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Analog-to-Digital Converter (ADC)
5.6 I/O Signals
The ADC module has six pins shared with port B, PTB5/AD5–PTB0/ATD0.
5.6.1 ADC Analog Power Pin (V_DDAD)/ADC Voltage Reference High Pin (V_REFH)
The ADC analog portion uses V_DDAD as its power pin. Connect the V_DDAD pin to the same voltage
potential as V_DD. External filtering may be necessary to ensure clean V_DDAD for good results.
NOTE
For maximum noise immunity, route V_DDAD carefully and place bypass
capacitors as close as possible to the package.
5.6.2 ADC Analog Ground Pin (V_SSAD)/ADC Voltage Reference Low Pin (V_REFL)
The ADC analog portion uses V_SSAD as its ground pin. Connect the V_SSAD pin to the same voltage
potential as V_SS.
5.6.3 ADC Voltage In (V_ADIN)
V_ADIN is the input voltage signal from one of the six ADC channels to the ADC module.
5.7 I/O Registers
These I/O registers control and monitor ADC operation:
• ADC status and control register (ADSCR)
• ADC data register (ADR)
• ADC clock register (ADCLK)
5.7.1 ADC Status and Control Register
Function of the ADC status and control register (ADSCR) is described here.
Address: $0003C
Bit 7
6
5
4
3
2
1
Read:
COCO
AIEN
ADCO ADCH4 ADCH3 ADCH2 ADCH1
Write:
Reset: 0
0
0
1
1
1
1
Figure 5-2. ADC Status and Control Register (ADSCR)
Bit 0
ADCH0
1
COCO — Conversions Complete Bit
When the AIEN bit is a logic 0, the COCO is a read-only bit which is set each time a conversion is
completed except in the continuous conversion mode where it is set after the first conversion. This bit
is cleared whenever the ADSCR is written or whenever the ADR is read.
If the AIEN bit is a logic 1, the COCO is a read/write bit which selects the CPU to service the ADC
interrupt request. Reset clears this bit.
1 = Conversion completed (AIEN = 0)
0 = Conversion not completed (AIEN = 0), or CPU interrupt (AIEN = 1)
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
58
Freescale Semiconductor