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CHAPTER 16 8/10-BIT A/D CONVERTER
MB90560 series
16.7 Usage Notes on the 8/10-Bit A/D Converter
Notes on using the 8/10-bit A/D converter.
I
Usage notes on the 8/10-bit A/D converter
G
Analog input pin
The A/D input pins are also used as the I/O pins of port 5. The port 5 data register (DDR5) and
analog input enable register (ADER) determine which pin is used for which purpose.
To use a pin as analog input, write “0” to the corresponding bit of DDR5 and change the port
setting to input. Then, set the analog input mode (ADEx = 1) in the ADER register and determine
the input gate of the port.
If an intermediate-level signal is input in the port input mode (ADEx = 0), a leakage current flows
through the gate.
G
Note on using an internal timer
To start the A/D converter with an internal timer, set the STS1 and STS0 bits of A/D control
status register 1 (ADCS1) accordingly. Set the input value of the internal timer at the inactive
level (L for the internal timer). Otherwise, operation may start concurrently with writing to the
ADCS register.
G
Sequence of turning on the A/D converter and analog input
Do not turn on power to the A/D converter (AVcc, AVR+, AVR-) and to the analog inputs (AN0 to
AN7) before the digital power supply (Vcc) has been turned on.
Do not turn off the digital power supply (Vcc) before power to the A/D converter and the analog
inputs has been turned off.
G
Supply voltage to the A/D converter
The supply voltage to the A/D converter (AVcc) must not exceed the digital power supply (Vcc);
otherwise, latchup may occur.