MC68HC908QY4A_10 Datasheet, PDF (192/200 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

• The ADC that is on the QYxA can operate while the MCU is in stop mode allowing lower power
operation. This also adds a lower noise environment for precise ADC results.
• Enabling an ADC channel no longer overrides the digital I/O function of the associated pin. To
prevent the digital I/O from interfering with the ADC read of the pin, the data direction bit associated
with the port pin must be set as input.
• Finally, the new ADC can be configured to select two different reference clock sources:
– The internal bus x 4
– An internal asynchronous source
The internal asynchronous clock source allows the ADC to be clocked for operation in stop mode.
A.2.1.1 Registers Affected
Read:
Write:
Reset:
Bit 7
COCO
0
6
5
AIEN
ADCO
0
0
= Unimplemented
4
ADCH4
1
3
ADCH3
1
2
ADCH2
1
1
ADCH1
1
Bit 0
ADCH0
1
Figure A-1. ADC10 Status and Control Register (ADSCR)
The ADCHx bits can be used to select additional ADC channels or bandgap measurement.
Bit 7
6
5
4
3
2
1
Bit 0
Read: 0
0
0
0
0
0
AD9
AD8
Write:
Reset: 0
0
0
0
0
0
0
0
= Unimplemented
Figure A-2. ADC10 Data Register High (ADRH), 10-Bit Mode
10-bit ADC uses the new ADRH register for the upper 2 bits.
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
ADLPC ADIV1 ADIV0 ADICLK MODE1 MODE0 ADLSMP
0
0
0
0
0
0
0
Figure A-3. ADC10 Clock Register (ADCLK)
Bit 0
ACLKEN
0
A long sample time option has been added to conserve power at the expense of longer conversion times.
This option is selected using the new ADLSMP bit in the ADCLK register. (The bit location was previously
reserved.)
The ADC will now run in stop mode if the ACLKEN bit is set to enable the asynchronous clock inside the
ADC module. Utilizing stop mode for an ADC conversion gives the quietest operating mode to get
extremely accurate ADC readings. (This bit location now used by ACLKEN was reserved — it always read
as a 0 and writes to that location had no affect.)
MC68HC908QYA/QTA Family Data Sheet, Rev. 3
192
Freescale Semiconductor