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| 型号： | ADC0851 |
| 厂商： | National Semiconductor Corporation |
| 英文描述： | 8-Bit Analog Data Acquisition and Monitoring Systems |
| 中文描述： | 8位模拟数据采集和监控系统 |
| 文件页数： | 26/36页 |
| 文件大小： | 581K |
| 代理商： | ADC0851 |
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4.0 A/D Conversion Modes
(Continued)
TABLE V(b). Channel Information
for One A/D Conversion (ADC0858)
Channel Information
Channels Enabled
I3
I2
I1
I0
0
0
0
0
CH0
0
0
0
1
CH0–CH1
0
0
1
0
CH1
0
0
1
1
Invalid
0
1
0
0
CH2
0
1
0
1
CH2–CH3
0
1
1
0
CH3
0
1
1
1
Invalid
1
0
0
0
CH4
1
0
0
1
CH4–CH5
1
0
1
0
CH5
1
0
1
1
Invalid
1
1
0
0
CH6
1
1
0
1
CH6–CH7
1
1
1
0
CH7
1
1
1
1
Invalid
The timing diagram for one A/D conversion is shown inFig-
ure 10. After CS goes low, the input word (DI) is clocked in
starting at the first rising edge of the digital clock signal,
CLK. The first four bits of the input word configure the de-
vice for ‘‘one A/D conversion’’ mode while the following
four bits (channel information address) assign the configura-
tion of the MUX as per Table V(a) and (b) for the ADC0851
and the ADC0858 respectively. Any input data following the
channel information address is ignored until the device’s
mode of operation is changed.
Taking CS high after the last bit of the channel information
address loads the input word. Had CS been kept low longer,
the following bits of the input word would have been ig-
nored. The device takes one to two OSC clock periods after
CS goes high to initiate the start of A/D conversion. The
EOC output goes low, thus signalling the start of the conver-
sion process. After a maximum of eighteen OSC clock peri-
ods, conversion is completed and EOC output goes high,
thus signalling the end of conversion. The output data is
now available and will be transmitted only if CS is brought
low. The output data is transmitted starting at the first rising
edge of CLK after CS goes low.
The format for the output word is as shown below.
Data Output (DO)DADC0851 or ADC0858
TL/H/11021–50
The first eight bits of the output word represent the digital
equivalent of the input voltage. Bits I3 through I0 provide the
channel configuration information as per Table V(a) and (b)
for ADC0851 and ADC0858 respectively. Note that this in-
formation is the same as the channel information in the in-
put word. The order in which the output data is transmitted
is as follows:
#
DataDLSB (D0) first
#
Channel informationDMSB (I3) first
Note that the output will be TRI-STATE if CS remains low
after I0 is transmitted. Taking CS high after the output data
is transmitted causes the device to initiate the start of the
next A/D conversion on the same input while ignoring the
data input word (DI). If the duration for which CS is high is
less than seventeen OSC clock periods, the conversion pro-
cess will be interrupted and the device will look for the mode
address at the falling edge of CS so as to configure to a new
mode of operation. However, if CS is high for eighteen or
more OSC clock periods then the conversion operation will
continue from point A on the timing diagram (Figure 10).
To ensure repetitive A/D conversion on the same input, CS
going low should be synchronized with EOC going high.
Thus after EOC goes high, the conversion is completed and
CS can go low to transmit the output data. Meanwhile, if CS
goes low while EOC is low then the conversion process is
interrupted and the device is readied for a new mode of
operation.
4.2 AUTO A/D CONVERSION MODE
When used in this mode, the ADC0851/8 offers added flexi-
bility that many multiplexed A/D converters don’t. In the
auto A/D conversion mode, the ADC0851/8 scans through
the selected input channels, performing A/D conversion on
each channel without the need for reloading a new data
input word each time. From Table I, the mode address for
the ‘‘Auto A/D Conversion’’ mode is 1 1 1 0.
The format for the input word is as follows:
Data Input (DI) WordDADC0851 or ADC0858
TL/H/11021–51
26
相关PDF资料 |
PDF描述 |
|---|---|
| ADC0851BIN | 8-Bit Analog Data Acquisition and Monitoring Systems |
| ADC0851BIV | 8-Bit Analog Data Acquisition and Monitoring Systems |
| ADC0851CIN | 8-Bit Analog Data Acquisition and Monitoring Systems |
| ADC0851CIV | 8-Bit Analog Data Acquisition and Monitoring Systems |
| ADC0858CIN | 8-Bit Analog Data Acquisition and Monitoring Systems |
相关代理商/技术参数 |
参数描述 |
|---|---|
| ADC0851 WAF | 制造商:Texas Instruments 功能描述: |
| ADC0851BIJ | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Single-Ended Data Acquisition System |
| ADC0851BIN | 制造商:NSC 制造商全称:National Semiconductor 功能描述:8-Bit Analog Data Acquisition and Monitoring Systems |
| ADC0851BIV | 制造商:NSC 制造商全称:National Semiconductor 功能描述:8-Bit Analog Data Acquisition and Monitoring Systems |
| ADC0851CIJ | 制造商:未知厂家 制造商全称:未知厂家 功能描述:Single-Ended Data Acquisition System |
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