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CHAPTER 18 8-/10-BIT A/D CONVERTER
Table 18.3-5 Function of A/D Setting Register (ADSR0/ADSR1) (1/2)
Bit Name Function
bit15
to
bit13
ST2, ST1, ST0:
Sampling time select
bits
These bits set the sampling time of A/D conversion.
• These bits set the time when the A/D conversion is started and
inputted analog voltage is sampled by the sample & hold circuit
until it is retained.
• See Table 18.3-6 for the setting of these bits.
bit12
to
bit10
CT2, CT1, CT0:
Comparing time
select bits
Comparing time of A/D conversion (comparing time) is set.
• These bits set the time when the analog input is A/D converted until
it stores to the data bits (D9 to D0).
• See Table 18.3-7 for the setting of these bits.
bit9,
bit4
Reserved bits Always write 0 to these bits. Reading value is always 0.
bit8
to
bit5
ANS3 to ANS0:
A/D conversion start
channel select bits
These bits set the channel at which A/D conversion start.At read, the
channel number under conversion can be checked if the A/D
conversion is in progress and last A/D converted channel number can
be checked if the A/D conversion is completed or is stopping.
And before A/D conversion starts, the previous conversion channel
will be read even if these bits have already been set to the new value.
These bits are initialized to "0000
B
" at reset.
Start channel < end channel:
A/D conversion starts at channel set by A/D conversion start channel
select bits (ANS3 to ANS0) and terminates channel set by A/D
conversion end channel select bits (ANE3 to ANE0)
Start channel = end channel:
A/D conversion is performed only for one channel set by A/D
conversion start (= end) channel select bits (ANS3 to ANS0 = ANE3
to ANE0)
Start channel > end channel:
Do not set
Continuous conversion mode and pause-conversion mode:
When A/D conversion terminated at the channel set by the A/D
conversion end channel select bits (ANE3 to ANE0), it returns to the
channel set by the A/D conversion start channel select bits (ANS3 to
ANS0).
Read (Other than pause-conversion mode) :
The channel numbers (15 to 0) under A/D conversion are read.
Read (Pause-conversion mode) :
At read during a pause, the channel number A/D-converted
immediately before a pause is read.
Notes:
• Do not set the A/D conversion start channel bits (ANS3 to ANS0)
during A/D conversion.
• Access in units of word when writing to these bits. If the byte write
or bit operation is performed, the A/D conversion may be started
from unexpected channel.