Renesas rl78 User Manual
RL78/G1A
CHAPTER 11 A/D CONVERTER
R01UH0305EJ0200 Rev.2.00
344
Jul 04, 2013
(5) Successive approximation register (SAR)
The SAR register is a register that sets voltage tap data whose values from the comparison voltage generator match
the voltage values of the analog input pins, 1 bit at a time starting from the most significant bit (MSB).
If data is set in the SAR register all the way to the least significant bit (LSB) (end of A/D conversion), the contents of
the SAR register (conversion results) are held in the A/D conversion result register (ADCR). When all the specified
A/D conversion operations have ended, an A/D conversion end interrupt request signal (INTAD) is generated.
(6) 12-bit A/D conversion result register (ADCR)
The A/D conversion result is loaded from the successive approximation register to this register each time A/D
conversion is completed, and the ADCR register holds the A/D conversion result in its lower 12 bits (the higher 4 bits
are fixed to 0).
(7) 8-bit A/D conversion result register (ADCRH)
The A/D conversion result is loaded from the successive approximation register to this register each time A/D
conversion is completed, and the ADCRH register stores the higher 8 bits of the A/D conversion result.
(8) Controller
This circuit controls the conversion time of an input analog signal that is to be converted into a digital signal, as well
as starting and stopping of the conversion operation. When A/D conversion has been completed, this controller
generates an interrupt request signal (INTAD) through the A/D conversion result upper limit/lower limit comparator.
(9) AV
REFP
pin
This pin inputs an external reference voltage (AV
REFP
).
If using AV
REFP
as the + side reference voltage of the A/D converter, set the ADREFP1 and ADREFP0 bits of A/D
converter mode register 2 (ADM2) to 0 and 1, respectively.
The analog signals input to ANI2 to ANI12 and ANI16 to ANI30 are converted to digital signals based on the voltage
applied between AV
REFP
and the
− side reference voltage (AV
REFM
/AV
SS
).
In addition to AV
REFP
, it is possible to select AV
DD
, or the internal reference voltage (1.45 V) as the + side reference
voltage of the A/D converter.
(10) AV
REFM
pin
This pin inputs an external reference voltage (AV
REFM
). If using AV
REFM
as the
− side reference voltage of the A/D
converter, set the ADREFM bit of the ADM2 register to 1.
In addition to AV
REFM
, it is possible to select AV
SS
as the
− side reference voltage of the A/D converter.