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Rev. 1.6
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C8051F310/1/2/3/4/5/6/7
5.3.2. Tracking Modes
According to Table 5.1, each ADC0 conversion must be preceded by a minimum tracking time for the con-
verted result to be accurate. The AD0TM bit in register ADC0CN controls the ADC0 track-and-hold mode.
In its default state, the ADC0 input is continuously tracked, except when a conversion is in progress. When
the AD0TM bit is logic 1, ADC0 operates in low-power track-and-hold mode. In this mode, each conversion
is preceded by a tracking period of 3 SAR clocks (after the start-of-conversion signal). When the CNVSTR
signal is used to initiate conversions in low-power tracking mode, ADC0 tracks only when CNVSTR is low;
conversion begins on the rising edge of CNVSTR (see Figure 5.4). Tracking can also be disabled (shut-
down) when the device is in low power standby or sleep modes. Low-power track-and-hold mode is also
useful when AMUX settings are frequently changed, due to the settling time requirements described in
Section “5.3.3. Settling Time Requirements” on page 54.
Figure 5.4. 10-Bit ADC Track and Conversion Example Timing
Write '1' to AD0BUSY,
Timer 0, Timer 2,
Timer 1, Timer 3 Overflow
(AD0CM[2:0]=000, 001,010
011, 101)
AD0TM=1
Track
Convert
Low Power Mode
AD0TM=0
Track or
Convert
Convert
Track
Low Power
or Convert
SAR Clocks
1234
56789
10
11
12
1234
56789
SAR Clocks
B. ADC0 Timing for Internal Trigger Source
1234
56789
CNVSTR
(AD0CM[2:0]=100)
AD0TM=1
A. ADC0 Timing for External Trigger Source
SAR Clocks
Track or Convert
Convert
Track
AD0TM=0
Track
Convert
Low Power
Mode
Low Power
or Convert
10
11
13
14
10
11
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