MC68HLC908QY4 Datasheet, PDF (43/182 Pages) Motorola, Inc – Microcontrollers

Input/Output Signals
3.6 Input/Output Signals
The ADC module has four channels that are shared with I/O port A.
ADC voltage in (ADCVIN) is the input voltage signal from one of the four ADC channels to the ADC
module.
3.7 Input/Output 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 (ADSCR). When a
conversion is in process and the ADSCR is written, the current conversion data should be discarded to
prevent an incorrect reading.
Address: $003C
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
In non-interrupt mode (AIEN = 0), COCO is a read-only bit that is set at the end of each conversion.
COCO will stay set until cleared by a read of the ADC data register. Reset clears this bit.
In interrupt mode (AIEN = 1), COCO is a read-only bit that is not set at the end of a conversion. It
always reads as a 0.
1 = Conversion completed (AIEN = 0)
0 = Conversion not completed (AIEN = 0) or CPU interrupt enabled (AIEN = 1)
NOTE
The write function of the COCO bit is reserved. When writing to the ADSCR
register, always have a 0 in the COCO bit position.
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 ADR is read or ADSCR 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 ADR 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
MC68HLC908QY/QT Family Data Sheet, Rev. 3
Freescale Semiconductor
43