C8051F336_08 Datasheet, PDF (39/227 Pages) Silicon Laboratories – Mixed-Signal Byte-Programmable EPROM MCU

C8051F336/7/8/9
complete. The falling edge of AD0BUSY triggers an interrupt (when enabled) and sets the ADC0 interrupt
flag (AD0INT). Note: When polling for ADC conversion completions, the ADC0 interrupt flag (AD0INT)
should be used. Converted data is available in the ADC0 data registers, ADC0H:ADC0L, when bit AD0INT
is logic 1. Note that when Timer 2 or Timer 3 overflows are used as the conversion source, Low Byte over-
flows are used if Timer 2/3 is in 8-bit mode; High byte overflows are used if Timer 2/3 is in 16-bit mode.
See Section “24. Timers” on page 180 for timer configuration.
Important Note About Using CNVSTR: The CNVSTR input pin also functions as Port pin P0.6. When the
CNVSTR input is used as the ADC0 conversion source, Port pin P0.6 should be skipped by the Digital
Crossbar. To configure the Crossbar to skip P0.6, set to ‘1’ Bit6 in register P0SKIP. See Section “20. Port
Input/Output” on page 119 for details on Port I/O configuration.
7.2.2. Tracking Modes
Each ADC0 conversion must be preceded by a minimum tracking time in order for the converted result to
be accurate. Refer to Section “6. Electrical Characteristics” on page 27 for minimum tracking time
specifications. 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; conver-
sion begins on the rising edge of CNVSTR (see Figure 7.2). Tracking can also be disabled (shutdown)
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
“7.2.3. Settling Time Requirements” on page 40.
CNVSTR
(AD0CM[2:0]=100)
SAR Clocks
A. ADC0 Timing for External Trigger Source
1 2 3 4 5 6 7 8 9 10 11 12 13 14
AD0TM=1
Low Power
or Convert
Track
Convert
Low Power
Mode
AD0TM=0
Track or Convert
Convert
Track
Write '1' to AD0BUSY,
Timer 0, Timer 2,
Timer 1, Timer 3 Overflow
(AD0CM[2:0]=000, 001,010
011, 101)
SAR
Clocks
AD0TM=1
B. ADC0 Timing for Internal Trigger Source
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
Low Power
or Convert
Track
Convert
Low Power Mode
SAR
Clocks
AD0TM=0
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Track or
Convert
Convert
Track
Figure 7.2. 10-Bit ADC Track and Conversion Example Timing
Rev.1.0
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