s908qc16vdse Freescale Semiconductor, Inc, s908qc16vdse Datasheet - Page 48

• Manufacturer Part Number: s908qc16vdse
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Analog-to-Digital Converter (ADC10) Module
clocks are too fast, then the clock must be divided to the appropriate frequency. This divider is specified
by ADIV[1:0] and can be divide-by 1, 2, 4, or 8.
3.3.2 Input Select and Pin Control
Only one analog input may be used for conversion at any given time. The channel select bits in ADSCR
are used to select the input signal for conversion.
3.3.3 Conversion Control
Conversions can be performed in either 10-bit mode or 8-bit mode as determined by the MODE bits.
Conversions can be initiated by either a software or hardware trigger. In addition, the ADC10 module can
be configured for low power operation, long sample time, and continuous conversion.
3.3.3.1 Initiating Conversions
A conversion is initiated:
If continuous conversions are enabled a new conversion is automatically initiated after the completion of
the current conversion. In software triggered operation, continuous conversions begin after ADSCR is
written and continue until aborted. In hardware triggered operation, continuous conversions begin after a
hardware trigger event and continue until aborted.
3.3.3.2 Completing Conversions
A conversion is completed when the result of the conversion is transferred into the data result registers,
ADRH and ADRL. This is indicated by the setting of COCO. An interrupt request is generated if AIEN is
set at the time that COCO is set.
A blocking mechanism prevents a new result from overwriting previous data in ADRH and ADRL if the
previous data is in the process of being read while in 10-bit mode (ADRH has been read but ADRL has
not). In this case the data transfer is blocked, COCO is not set, and the new result is lost. When a data
transfer is blocked, another conversion is initiated regardless of the state of ADCO (single or continuous
conversions enabled). If single conversions are enabled, this could result in several discarded
conversions and excess power consumption. To avoid this issue, the data registers must not be read after
initiating a single conversion until the conversion completes.
3.3.3.3 Aborting Conversions
Any conversion in progress will be aborted when:
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Following a write to ADSCR (with ADCH bits not all 1s) if software triggered operation is selected.
Following a hardware trigger event if hardware triggered operation is selected.
Following the transfer of the result to the data registers when continuous conversion is enabled.
A write to ADSCR occurs (the current conversion will be aborted and a new conversion will be
initiated, if ADCH are not all 1s).
A write to ADCLK occurs.
The MCU is reset.
The MCU enters stop mode with ACLK not enabled.
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 4
Freescale Semiconductor