Fujitsu FR81S User Manual
CHAPTER 44: 12-BIT A/D CONVERTER
5. Operation
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER
: 12-BIT A/D CONVERTER
FUJITSU SEMICONDUCTOR CONFIDENTIAL
114
5.4.7. A/D Conversion Time
The A/D conversion time is shown.
The A/D conversion time is between total time of the sampling time and the compare time.
Sampling time
The sampling time can select either of each channel or a common setting by the sampling time setting per
channel enable bit (ADMD.STPCEN).
When STPCEN="0", all channels are common the sampling time. The sampling time is set by the
sampling time set bit (ADMD.ST1,ST0).
When STPCEN="1", the sampling time of each channel can be set. The sampling time of each channel is
set by the sampling time setting per channel enable bit (ADSTPCS.STCHn1, STCHn0: n=00 to 47).
Table 5-12 Sampling time to peripheral clock frequency
ST1,
STCHn1
ST0,
STCHn0
Function
Sampling time (Peripheral clock frequency)
(40MHz) (32MHz) (24MHz) (16MHz)
0
0
12 Peripheral clock
300ns
375ns
500ns
750ns
0
1
18 Peripheral clock
450ns
562.5ns
750ns
1125ns
1
0
24 Peripheral clock
600ns
750ns
1000ns
1500ns
1
1
48 Peripheral clock
1200ns
1500ns
2000ns
3000ns
Note:
Please set the sampling time to 700ns(4.5V to 5.5V)/1000ns(2.7V to 5.5V) or more. When the sampling
time is set to 700ns/1000ns or less, a normal value of the analog conversion value might not be obtained.
Please rewrite these bits when the A/D operation has stopped before conversion operation.
Compare time
The compare time is set to compare time set bit (ADMD.CT1,CT0).
Table 5-13 Sampling time to peripheral clock frequency
CT1
CT0
Function
Compare time (Peripheral clock frequency)
(40MHz) (32MHz) (24MHz) (16MHz)
0
0
28 Peripheral clock
700ns
875ns
1166.7ns
1750ns
0
1
42 Peripheral clock
1050ns
1312.5ns
1750ns
2625ns
1
0
56 Peripheral clock
1400ns
1750ns
2333.4ns
3500ns
1
1
112 Peripheral clock
2800ns
3500ns
4666.7ns
7000ns
Note:
Please set the compare time to 700ns or more. When the compare time is set to 700ns or less, a normal
value of the analog conversion value might not be obtained.
Please rewrite these bits when the A/D operation has stopped before conversion operation.
MB91520 Series
MN705-00010-1v0-E
1917