UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 420

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

14.3 OPERATION
14.3.1 Basic A/D Converter Operation
(1) A/D Conversion Operation procedure
380
A/D conversion is performed by means of the following procedure:
(a) Analog pin selection and operating mode specification are set with the A/D converter mode register (ADM).
(b) Bit 7 (CS) of the ADM is set (1), and A/D conversion is started.
(c) When conversion starts, the MSB (bit 7) of the successive approximation register (SAR) is set (1) automatically.
(d) When bit 7 of the SAR is set (1), the tap selector sets the series resistor string voltage tap to
(e) The voltage difference between the series resistor string voltage tap and the analog input is determined by the
(f) Next, bit 6 of the SAR is set (1) automatically, and the next comparison is performed. Here, the series resistor
(g) The same kind of comparison is continued up to the LSB (bit 0) of the SAR (binary search method).
voltage comparator. If the analog input is greater than (1/2) AV
it is less than (1/2) AV
string voltage tap is selected according to the value of bit 7 for which the result has already been set, as shown
below.
• Bit 7 = 1 ........
• Bit 7 = 0 ........
This voltage tap is compared with the analog input voltage, and bit 6 of the SAR is manipulated as follows according
to the result:
• Analog input voltage
• Analog input voltage < voltage tap: Bit 6 = 0
255
512
AV
REF1
(= 1/2 AV
.
.
383
512
127
512
REF1
REF1
AV
AV
, the MSB is cleared (0).
voltage tap: Bit 6 = 1
).
REF1
REF1
.
.
=
=
.
.
CHAPTER 14 A/D CONVERTER
3
4
1
4
AV
AV
REF1
REF1
REF1
, the MSB of the SAR remains set (1), and if