MC68HC908AS32A Datasheet, PDF (63/280 Pages) Freescale Semiconductor, Inc – Microcontrollers

I/O Registers
3.6.2 ADC Analog Ground Pin (V_SSA)/ADC Voltage Reference Low Pin (V_REFL)
The ADC analog portion uses V_SSA as its ground pin. Connect the V_SSA pin to the same voltage potential
as V_SS. V_REFL is the lower reference supply for the ADC.
3.6.3 ADC Voltage In (ADCVIN)
ADCVIN is the input voltage signal from one of the 15 ADC channels to the ADC module.
3.7 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 (ADICLK)
3.7.1 ADC Status and Control Register
The following paragraphs describe the function of the ADC status and control register.
Address: $0038
Bit 7
6
5
4
3
2
1
Bit 0
Read: COCO
AIEN
ADCO
CH4
CH3
CH2
CH1
CH0
Write: R
Reset: 0
0
0
1
1
1
1
1
R
= Reserved
Figure 3-3. ADC Status and Control Register (ADSCR)
COCO — Conversions Complete Bit
When the AIEN bit is a 0, the COCO is a read-only bit which is set each time a conversion is completed.
This bit is cleared whenever the ADC status and control register is written or whenever the ADC data
register is read.
If the AIEN bit is a 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 enabled (AIEN = 1)
AIEN — ADC Interrupt Enable Bit
When this bit is set, an interrupt is generated at the end of an ADC conversion. The interrupt signal is
cleared when the data register is read or the status/control register is written. Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the ADR register at the end of each
conversion. Only one conversion is allowed when this bit is cleared. Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
MC68HC908AS32A Data Sheet, Rev. 2.0
Freescale Semiconductor
63