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Renesas Electronics America - Knowledgebase

What's the difference between 8 bit A/D and 10 bit A/D converter?

Latest Updated:12/01/2011


Microcontrollers with an on-chip 8-bit A/D converter and microcontrollers with an on-chip 10-bit A/D converter are supported by the same flash version microcontroller, but how are they differentiated?


This applies the following subseries.

uPD78F0034A for uPD780024A/0034A Subseries
uPD78F9116A for uPD789104A/9114 Subseries
uPD78F9136A for uPD789124A/9134A Subseries
uPD78F9177 for uPD789167/9177 Subseries
uPD78F9418A for uPD789407A/9417A Subseries
uPD78F9436 for uPD789426/9436 Subseries
uPD78F9456 for uPD789446/9456 Subseries

For these products, the same flash version microcontroller is used to evaluate mask version microcontrollers with an on-chip 8-bit A/D converter and those with an on-chip 10-bit A/D converter.
For this purpose, the mapping of the result register and bit configuration have been specialized.

10-bit result data is stored in the higher 10 bits of a 16-bit register, and this 16-bit register is mapped as follows.
Addr0 : The lower 2 bits of the 10-bit result are stored in bits 7 and 6
Addr0+1 : Stores the higher 8 bits of the 10-bit result

When evaluating a 10-bit A/D converter, read from Addr0 using a 16-bit transfer instruction (MOVW) and obtain a 10-bit result from the higher 10 bits of the 16-bit register.

When evaluating an 8-bit A/D converter, read from Addr0+1 using an 8-bit transfer instruction (MOV) and obtain an 8-bit result from the 8-bit register.

In actual programming, 8-bit A/D converter or 10-bit A/D converter is determined when the target device is specified (based on the device file).

Since the address and word/byte configuration are automatically determined when the conversion result register (ADCR0) is specified, it is not necessary to be aware of which address to access.
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