Notes On The 8/10-Bit A/D Converter - Fujitsu MB90390 Series Hardware Manual

CHAPTER 18 8/10-BIT A/D CONVERTER
18.7

Notes on the 8/10-Bit A/D Converter

Notes on using the 8/10-bit A/D converter.
■ Usage Notes on the 8/10-bit A/D Converter
●
Analog input pin
The A/D input pins are also used as the I/O pins of ports 6 and B. The corresponding Data Direction
Register (DDR6 and DDRB) and the 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 DDR6, resp. of DDRB, and thereby
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.
●
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.
●
Sequence of turning on the A/D converter and analog input
Do not turn on power to the A/D converter (AV
before the digital power supply (V
Do not turn off the digital power supply (V
been turned off.
●
Supply voltage to the A/D converter
The supply voltage to the A/D converter (AV
otherwise, latch-up may occur.
300
, AVRH, AVRL) and to the analog inputs (AN0 to AN7)
CC
) has been turned on.
CC
) before power to the A/D converter and the analog inputs has
CC
) must not exceed the digital power supply (V
CC
);
CC