Fujitsu MB91150 Series, Hardware Manual, Page: 309 / 512

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CHAPTER 13 8/10-BIT A/D CONVERTER
13.8 Notes on Using the 8/10-bit A/D Converter
This section provides notes on using the 8/10-bit A/D converter.
■
Notes on using the 8/10-bit A/D converter
❍
Analog input pin
The A/D input pins are also used as I/O pins for port K. The pins are switched using the port K
direction register (DDRK) and analog input permission register (AICK). For a pin to be used for
analog input, set the DDRK bit corresponding to the pin to 0 to set the pin as the input port, then
specify the analog input mode (AIx = 1) using the AICK register to fix the input gate for the port.
While port input mode (AIx = 0) is set, the input leak current flows to the gate if an intermediate
level signal is input.
❍
Note on using the A/D converter with the internal timer
To start the A/D converter with the internal timer, specify the STS1 and STS0 bits of A/D control
status register 1 (ADCS1) and also set the value for internal timer inputs to inactive (L for the
internal timer). When it is set to active, the internal timer may start operating as soon as a write
operation to the ADCS register is performed.
❍
Priorities of A/D converter power and analog input
Be sure to apply the power to the A/D converter (AV
CC
, AVR+, AVR-) and analog input (AN0 to
AN7) after or as soon as the digital power supply (V
CC
) is turned on. Also, be sure to turn off the
digital power (V
CC
) after or as soon as the power to the A/D converter and analog input are cut.
❍
Voltage of the A/D converter
To prevent a latch-up, set an A/D converter voltage (AV
CC
) that does not exceed the voltage of
the digital circuit (V
CC
).