CHAPTER 11 10-BIT A/D CONVERTER (
µ
PD789436 AND 789456 SUBSERIES)
User’s Manual U15075EJ2V1UD
202
Figure 11-1. Block Diagram of 10-Bit A/D Converter
Sample & hold circuit
Voltage comparator
Successive
approximation
register (SAR)
Controller
3
A/D conversion result
register 0 (ADCR0)
Tap selector
AV
SS
INTAD0
A/D converter mode
register 0 (ADM0)
Analog input channel
specification register 0 (ADS0)
Internal bus
AV
SS
P-ch
AV
DD
ANI4/P64
ANI5/P65
ANI0/P60
ANI1/P61
ANI2/P62
ANI3/P63
Selector
ADCS0 FR02
FR01
FR00
ADS02 ADS01 ADS00
(1) Successive approximation register (SAR)
The SAR receives the result of comparing an analog input voltage and a voltage at a voltage tap
(comparison voltage), received from the series resistor string, starting from the most significant bit (MSB).
Upon receiving all the bits, down to the least significant bit (LSB), that is, upon the completion of A/D
conversion, the SAR sends its contents to A/D conversion result register 0 (ADCR0).
(2) A/D conversion result register 0 (ADCR0)
ADCR0 is a 16-bit register that holds the result of A/D conversion. The lower 6 bits are fixed to 0. Each time
A/D conversion ends, the conversion result in the successive approximation register is loaded into ADCR0.
The higher 8 bits of the conversion result are loaded into FF15H of ADCR0 and the lower 2 bits into FF14H,
with the bit 15 as the most significant bit (MSB).
ADCR0 can be read with a 16-bit memory manipulation instruction.
RESET input sets ADCR0 to 0000H.
ADCR0
Symbol
FF15H
0
0
0
0
0
0
FF14H
FF14H,
FF15H
Address After reset
0000H
R/W
R
Caution When
the
µ
PD78F9436, a flash memory version of the
µ
PD789425 or
µ
PD789426, is used,
this register can be accessed in 8-bit units. However, only an object file assembled with
the
µ
PD789425 or
µ
PD789426 can be used. The same is also true for the
µ
PD78F9456, a
flash memory version of the
µ
PD789445 or
µ
PD789446: This register can be accessed in 8-
bit units, but only an object file assembled with the
µ
PD789445 or
µ
PD789446 can be used.
Содержание U789436 Series
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