AMC7823 Datasheet, PDF (37/48 Pages) Texas Instruments – ANALOG MONITORING AND CONTROL CIRCUIT

AMC7823
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REGISTERS
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.
AMC Status/Configuration Register (Read/Write; see Figure 50, DAV Pin and GALR Pin)
Bit 15
MSB
X
Bit 14
RSTC
Bit 13
DAVF
Bit 12
0
Bit 11
X
Bit 10
X
Bit 9
X
Bit 8
X
Bit 7
SREF
Bit 6
GREF
Bit 5
ECNVT
Bit 4
X
Bit 3
X
Bit 2
X
Bit 1
X
Bit 0
LSB
X
X : Don't Care
RSTC
DAVF
Bit 12
SREF
GREF
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.
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.
Read-only. Always '0'.
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-kΩ 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-kΩ
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'.
Gain of the internal reference voltage (V_REF). 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.
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