MC9S12C Datasheet, PDF (247/680 Pages) Motorola, Inc – 16-Bit Microcontroller

Chapter 8 Analog-to-Digital Converter (ATD10B8C) Block Description
8.4.2.2 General-Purpose Digital Port Operation
The channel pins can be multiplexed between analog and digital data. As analog inputs, they are
multiplexed and sampled to supply signals to the A/D converter. Alternatively they can be configured as
digital I/O signals with the port I/O data being held in PORTAD.
The analog/digital multiplex operation is performed in the pads. The pad is always connected to the analog
inputs of the ATD10B8C. The pad signal is buffered to the digital port registers. This buffer can be turned
on or off with the ATDDIEN register. This is important so that the buffer does not draw excess current
when analog potentials are presented at its input.
8.4.2.3 Low-Power Modes
The ATD10B8C can be configured for lower MCU power consumption in three different ways:
1. Stop Mode: This halts A/D conversion. Exit from Stop mode will resume A/D conversion, But due
to the recovery time the result of this conversion should be ignored.
2. Wait Mode with AWAI = 1: This halts A/D conversion. Exit from Wait mode will resume A/D
conversion, but due to the recovery time the result of this conversion should be ignored.
3. Writing ADPU = 0 (Note that all ATD registers remain accessible.): This aborts any A/D
conversion in progress.
NOTE
The reset value for the ADPU bit is zero. Therefore, when this module is
reset, it is reset into the power down state.
8.5 Initialization/Application Information
8.5.1 Setting up and starting an A/D conversion
The following describes a typical setup procedure for starting A/D conversions. It is highly recommended
to follow this procedure to avoid common mistakes.
Each step of the procedure will have a general remark and a typical example
8.5.1.1 Step 1
Power up the ATD and concurrently define other settings in ATDCTL2
Example: Write to ATDCTL2: ADPU=1 -> powers up the ATD, ASCIE=1 enable interrupt on finish of a
conversion sequence.
8.5.1.2 Step 2
Wait for the ATD Recovery Time t_REC before you proceed with Step 3.
Example: Use the CPU in a branch loop to wait for a defined number of bus clocks.
Freescale Semiconductor
MC9S12C-Family / MC9S12GC-Family
247
Rev 01.23