AMC7832_15 Datasheet, PDF (31/72 Pages) Texas Instruments – AMC7832 12-Bit Analog Monitor and Control Solution with Multi-Channel ADC, Bipolar DACs, Temperature Sensor and GPIO Ports

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AMC7832
SLAS836 – MARCH 2014
8.3.2.3 ADC Synchronization
A trigger signal is required for getting the ADC in and out of idle state. The ADC trigger can be generated either
through software (ICONV bit in the ADC Trigger Register, 0xC0) or hardware (GPIO2/ADCTRIG, terminal 11). In
order to use the GPIO2/ADCTRIG terminal as an ADC trigger, the terminal must be configured accordingly in the
GPIO Configuration register (address 0x12). When the terminal is configured as a trigger, a falling edge starts
the sampling and conversion of the ADC.
The ADC Data registers (0x20 – 0x41) and Temperature Data registers (0x78 – 0x79) should only be accessed
while the ADC is in idle state or between conversion sequences if the ADC is in auto-mode. A data available
indicator signal is generated by the device to track the ADC status. Failure to satisfy the synchronization
requirements could lead to erroneous data reads.
The data available indicator signal is output through the GPIO3/DAV terminal. The GPIO3/DAV terminal must be
configured in the GPIO Configuration register (address 0x12) as an interrupt. In addition to the terminal indicator
the device provides a data available flag accessible through the serial interface (DAVF bit in the General Status
Register, 0x72). The DAV terminal is available in both auto and direct-mode but the DAVF flag is only available
in direct mode.
The terminal and flag behavior are dependent on the conversion mode. In direct-mode, after the conversion is
completed and the ADC returns to idle state, the DAVF bit is set immediately to ‘1’ and the DAV terminal is active
(low) to indicate new data is available. The terminal and flag are cleared automatically once a new conversion is
started or one of the ADC Data or Temperature Data registers is accessed. In auto-mode, the DAVF bit is fixed
to ‘0’ and therefore synchronization is always done through the DAV terminal. After one auto-mode conversion
sequence is complete a 1µs pulse (low) is issued on the DAV terminal. When an auto-mode conversion needs to
be stopped it is recommended to do so in synchronization with DAV.
a) Direct-Mode, software trigger
CS
Trigger
Command
1^st internal
trigger
Read
Command
Trigger
Command
2^nd internal
trigger
Read
Command
DAV
1^st CONVERSION of the
channels specified in the ADC
MUX Registers
2^nd CONVERSION of the
channels specified in the ADC
MUX Registers
b) Auto-Mode, software trigger
CS
Trigger
Command
1^st internal
trigger
DAV
Read
Command
1µs
>4µs
Read
Command
1^st CONVERSION of the
channels specified in the ADC
MUX Registers
2^nd CONVERSION
Figure 45. ADC Software Trigger Synchronization
3^rd CONVERSION
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