Precautions When Using 8/10-Bit A/D Converter - Fujitsu F2MC-16LX Hardware Manual

CHAPTER 19 8/10-BIT A/D CONVERTER
19.5

Precautions when Using 8/10-bit A/D Converter

Precautions when using 8/10-bit A/D converter is indicated.
Precautions when Using 8/10-bit A/D Converter
Analog input pin
The A/D input terminal is in the common use with the input-output terminals of port 7 and port 8 to be used
by switching between the port 7 and port 8 direction register (DDR7 and DDR8) and the analog input
enable register (ADER). Write "0" to the corresponding bits of DDR7 and DDR8 to input the port setting
and set the analog input mode (ADEx = 1) to the ADER register to fix the port side input gate for terminals
to be used as analog input. When the intermediate level signal is input in the port input mode (ADEx = 0),
the input leak current flows through the gate.
Notes on using in Internal timer (16-bit reload timer 1)
Set the input value of internal timer to the inactive side ("L" for the internal timer) when setting the STS1
and STS0 bits of A/D control status register "H" level (ADCS1) to start the A/D converter by the internal
timer. When it is set to the active side, the operation may be started at the same time of writing on the
ADCS1 register.
Set the STS1 and STS0 in the status of the "1" input to the ADTG and the "0" output from the internal
timer (PPG1).
Turning-on sequence of power supply to A/D converter and analog inputs
Apply the A/D converter power supply (AVcc and AVRH) and the analog input (AN0 to AN15) always
after or simultaneously turning on the digital power supply (Vcc). In addition, turn off the A/D converter
power supply and the analog input after or simultaneously turn off the digital power supply (Vcc).
Power supply voltage of the A/D converter
Keep the A/D converter power supply voltage (AVcc) not to exceed the digital power supply voltage (Vcc)
to prevent the latch up.
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