Datasheet

ADC12130, ADC12132, ADC12138

www.ti.com

SNAS098G –MARCH 2000–REVISED MARCH 2013

Figure 66. Changing the ADC's Conversion Configuration

1.6 User Mode and Test Mode

An instruction may be issued to the ADC to put it into test mode, which is used by the manufacturer to verify

complete functionality of the device. During test mode CH0–CH7 become active outputs. If the device is

inadvertently put into the test mode with CS continuously low, the serial communications may be

desynchronized. Synchronization may be regained by cycling the power supply voltage to the device. Cycling the

power supply voltage will also set the device into user mode. If CS is used in the serial interface, the ADC may

be queried to see what mode it is in. This is done by issuing a “read STATUS register” instruction to the ADC.

When bit 9 of the status register is high, the ADC is in test mode; when bit 9 is low the ADC, is in user mode. As

an alternative to cycling the power supply, an instruction sequence may be used to return the device to user

mode. This instruction sequence must be issued to the ADC using CS. The following table lists the instructions

required to return the device to user mode. Note that this entire sequence, including both Test Mode and User

Mode values, should be sent to recover from the test mode.

DI Data

(1)

Instruction

DI0 DI1 DI2 DI3 DI4 DI5 DI6 DI7

TEST MODE H X X X H H H H

Reset L L L L H H H L

Test Mode

L L L L H L H L

Instructions

L L L L H L H H

USER MODE L L L L H H H H

Power Up L L L L H L H L

Set DO with or without Sign H or L L L L H H L H

Set Acquisition Time H or L H or L L L H H H L

Start a Conversion H or L H or L H or L H or L L H or L H or L H or L

(1) X = Don't Care

The power up, data with or without sign, and acquisition time instructions should be resent after returning to the

user mode. This is to ensure that the ADC is in the required state before a conversion is started.

1.7 Reading the Data Without Starting a Conversion

The data from a particular conversion may be accessed without starting a new conversion by ensuring that the

CONV line is taken high during the I/O sequence. See Figure 55 and Figure 56.Table 5 describes the operation

of the CONV pin. It is not necessary to read the data as soon as DOR goes low. The data will remain in the

output register ifCS is brought high right after DOR goes high. A single conversion may be read as many times

as desired before CS is brought low.

1.8 Brown Out Conditions

When the supply voltage dips below about 2.7V, the internal registers, including the calibration coefficients and

all of the other registers, may lose their contents. When this happens the ADC will not perform as expected or

not at all after power is fully restored. While writing the desired information to all registers and performing a

calibration might sometimes cause recovery to full operation, the only sure recovery method is to reduce the

supply voltage to below 0.5V, then reprogram the ADC and perform a calibration after power is fully restored.

Product Folder Links: ADC12130 ADC12132 ADC12138