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MB90420/5 (A) SERIES F
19.7 Precautions at Using 8-/10-bit A/D Converter
Precautions at using the 8-/10-bit A/D converter are given below:
n Precautions at using 8-/10-bit A/D converter
• Analog input pin
The A/D input pin also serves as the I/O pin of port 6; these two functions are used by switching with the
port 6 direction register (DDR6) and the analog input enable register (ADER). When using the pin as the
analog input, write 0 to the corresponding bit of DDR6 to set the port to input, and then set the analog input
mode (ADEx = 1) by using the ADER register in order to fix the input gate for the port side. When the port
input mode (ADEx = 0) is enabled, the input leakage current is fed through the gate when the middle level
signal is input.
• Precautions at using A/D converter via internal timer (16-bit reload timer 1)
When starting the A/D converter by using the internal timer, set using the STS1 and STS0 bits of the A/D
control status register higher (ADCSH). At this point, set the input value of the internal timer to Inactive (L
for internal timer). When it is set to active, operation may start concurrently with writing to the ADCSH
register.
• Power-on procedure of A/D converter power supply and analog input
Always turn on the A/D converter power (AV
concurrently with turning on the digital power (V
analog input before or concurrently with turning off the digital power (V
• Power supply voltage of A/D converter
To prevent latch up, do not allow the A/D converter power supply (AV
(V
) voltage.
CC
2
MC-16LX FAMILY 16-BIT MICROCONTROLLERS HARDWARE MANUAL
, AVRH) and the analog input (AN0 to AN7) after or
CC
). Always turn off the A/D converter power and the
CC
19-22
)
CC
) to exceed the digital power supply
CC
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