Input impedance of the analog input | Fujitsu F202RA, MB89202

CHAPTER 12 A/D CONVERTER

12.7Notes on Using A/D Converter

This section describes notes on using the A/D converter.

■Notes on Using the A/D Converter

●Input impedance of the analog input

The A/D converter contains the sample hold circuit as shown in Figure 12.7-1 , captures the voltage of the analog input, and holds it in the capacitor for sample hold in about 16 instruction cycles, after activation of A/D conversion. Accordingly, when the output impedance of the external circuit of the analog input is high, the analog input voltage may not be stabilized during analog input sampling period. Therefore, set the output impedance of the external circuit to a sufficiently low level (lower than about 4 kΩ). If the output impedance of the external circuit cannot be set low, it is recommended that a capacitor with about 0.1 ∝F be added externally to the analog input.

Figure 12.7-1 Equivalent Circuit of Analog Input

MB89202/F202RA series

AN0 to AN7

Selecting an analog channel

Sample hold circuit

Converter

R C

After activation of A/D conversion, close 16 instruction cycles

●Notes on setting using a program

•When A/D conversion functions are enabled, the values in the ADDH and ADDL registers are held without being changed until the activation of A/D conversion. However, once A/D conversion is activated, the values in the ADDH and ADDL registers become undefined immediately.

•When A/D conversion functions are enabled, do not reselect an analog input channel (ADC1: ANS3 to

ANS0). Especially, during continuous activation, disable continuous activation (ADC2: EXT = 0), and

wait for the conversion in-progress flag bit (ADC1: ADMV) to be "0" for reselection.

•The A/D converter is stopped via a reset and activation of the stop mode, and all registers are initialized.

•When the interrupt request flag bit (ADC1: ADI) is "1" and an interrupt request is enabled (ADC2: ADIE = 1), recovery from interrupt handling is no longer possible. Be sure to clear the ADI bit.

Note:

When A/D conversion is completed, if the next conversion is reactivated, the interrupt request flag bit (ADC1: ADI) is not set.

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F202RA, MB89202 specifications

The Fujitsu MB89202 and F202RA microcontrollers are part of the 16-bit microcontroller family, renowned for their robust performance and versatility in a variety of embedded system applications. These devices are tailored for high-efficiency operation across diverse industries, including automotive, consumer electronics, and industrial automation.

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Memory capacity is a vital characteristic of the MB89202, featuring on-chip RAM and ROM configurations. The microcontroller can accommodate different memory variants, providing developers with flexibility in memory allocation based on their application requirements. This adaptability facilitates applications ranging from simple control systems to complex data processing tasks.

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In summary, the Fujitsu MB89202 and F202RA microcontrollers stand out with their efficient performance, extensive memory options, integrated peripherals, and power-saving capabilities, making them ideal for a wide array of embedded applications. Their reliability and robustness further enhance their attractiveness for designers seeking advanced microcontroller solutions.

Fujitsu F202RA, MB89202 manual This section describes notes on using the A/D converter

Models: F202RA MB89202