MB89960 series
CHAPTER 11 A/D Converter
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q Clock selector
Selects the clock used to activate A/D conversion when continuous activation is enabled (ADC2:
EXT = “1”).
q Analog channel selector
This circuit selects one of the four analog input channels.
q Sample and hold circuit
This circuit holds the input voltage of the channel selected by the analog channel selector. The
circuit samples and holds the input voltage immediately after the A/D conversion is activated.
This allows A/D conversion to proceed without being affected by input voltage variation.
q D/A converter
Generates the voltage corresponding to the value set in the ADDL and ADDH registers.
q Comparator
Compares the sampled and held input voltage with the output voltage of the D/A converter, and
determines which voltage is higher or lower.
q Control circuit
The control circuit successively determines the value of each bit of the ADDL and ADDH
registers, starting from the most significant bit and proceeding to the least significant bit, based
on the greater-than/less-than signal from the comparator. When conversion is complete, the
circuit sets the interrupt request flag bit (ADC1: ADI).
q ADDL and ADDH registers
The ADDL (lower 8 bits) and ADDH (upper 2 bits) registers stores the A/D conversion result .
q ADC1 register
Used to enable or disable each function, select the analog input pin, check statuses, and control
interrupts.
q ADC2 register
Uses include selecting the input clock, enabling or disabling interrupts, and selecting functions.
s A/D Converter Supply Voltage
q AVcc
The A/D converter power supply pin. Use at the same voltage level as Vcc. When high A/D
conversion accuracy is required, take measures to ensure that the noise on Vcc is not present
on AVcc, or use a separate power supply. Connect this pin to the power supply, even if the A/D
converter is not used.
q AVss
The A/D converter ground pin. Use at the same voltage as Vss. When high A/D conversion
accuracy is required, take measures to ensure that the noise on Vss is not present on AVss.
Connect this pin to ground (GND), even if the A/D converter is not used.
q AVR
Reference voltage input pin for the A/D converter. The A/D converter performs 10-bit A/D
conversion between AVR and AVss.
Connect to AVss if the A/D converter is not used.