AMC7823 datasheet(37/48 Pages) TI

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REGISTERS

AMC Status/Configuration Register (Read/Write; see Figure 50, DAV Pin and GALR Pin)

AMC7823

SLAS453A – APRIL 2005 – REVISED OCTOBER 2005

This section describes each of the registers shown in the memory map of Table 2. The registers are named

descriptively, according to their respective functions.

NOTE: After power-on or reset, all ADC channels, all DACs, and the precision current source are in a

powered-down state. The user must write the Power-Down Register properly in order to activate the desired

components. For details, see the Power-Down Register section.

Bit 15

Bit 14

Bit 13

Bit 12

Bit 11

Bit 10

Bit 9

Bit 8

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

MSB

LSB

RSTC

DAVF

SREF

GREF

ECNVT

X : Don't Care

RSTC

RESET Complete Bit. This bit is set to '1' on power-up or reset. This bit can be cleared by writing

'0' to this location. The host cannot set this bit to '1'. This bit allows the host to determine if the

part has been configured after power-up, or if a reset has occurred to the AMC7823 without

knowledge of the host.

DAVF

ADC Data Available Flag. For direct-mode only. Always cleared (set to '0') in auto-mode (see ADC

Control Register).

DAVF = 1: The ADC conversions are complete and new data are available.

DAVF = 0: The ADC conversion is in progress (data is not ready) or the ADC is in Auto-Mode.

In direct-mode, bit DAVF sets the pin DAV. DAV goes low when DAVF = 1, and goes high when

DAVF = 0. In auto-mode, DAVF is always cleared to '0'. However, a 2-

µs pulse (active low)

appears on the DAV pin when the input with ending address [EA3:EA0] is converted. DAVF is

cleared to '0' in one of three ways: (1) reading the ADC Data Register; (2) starting a new ADC

conversion; or (3) writing '0' to this bit.

Bit 12

Read-only. Always '0'.

SREF

Select Reference bit.

SREF = 0 (default condition): The internal reference is selected as the chip reference. It is

connected to pin 21, EXT_REF_IN, by a 10-k

Ω resistor.

SREF = 1: The internal reference is de-selected and disconnected from pin 21 (EXT_REF_IN).

Pin 21 floats unless an external reference is applied. Always set SREF bit to '1' when an external

reference is applied; otherwise, the external reference must sink or source current. The current

value is the voltage difference between the external and internal reference divided by a 10-k

Ω

resistance.

SREF also provides information to the precision current source and is used to configure that

source (see the Precision Current Source section for details). After power-on or reset, SREF is

cleared to '0'.

GREF

Gain of the internal reference voltage (VREF). This bit selects one of two preset values for the

internal reference voltage, but has no effect on the external reference. GREF also provides

information to the precision current source and is used to configure that source (see the Precision

Current Source section for details).

GREF = 0: The internal reference voltage is +1.25 V.

GREF = 1: The internal reference voltage is +2.5 V.

AMC7823 Datasheet(PDF) 37 Page - Texas Instruments

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