AMC7823 Datasheet, PDF (40/48 Pages) Texas Instruments – ANALOG MONITORING AND CONTROL CIRCUIT

AMC7823
SLAS453A – APRIL 2005 – REVISED OCTOBER 2005
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ADC Control Register (Read/Write; see ADC Operation and AMC Status/Configuration Register)
This register specifies the ADC conversion mode and identifies the analog inputs to be converted. A write
command to this register initiates conversion when the internal ADC trigger is selected (bit ECNVT = 0 in the
AMC Status/Configuration Register). However, when the external trigger is selected (bit ECNVT = 1), a write
command to this register does not start the conversion, but it does identify the analog inputs to be converted.
Internal trigger mode may employ either direct- or auto-mode conversion.
Bit 15
MSB
CMODE
Bit 14
X
Bit 13
X
Bit 12
X
Bit 11
SA3
Bit 10
SA2
Bit 9
SA1
Bit 8
SA0
Bit 7
EA3
Bit 6
EA2
Bit 5
EA1
Bit 4
EA0
Bit 3
X
Bit 2
X
Bit 1
X
Bit 0
LSB
X
X : Don't Care
CMODE
SA3–SA0
EA3–EA0
ADC Conversion Mode bit. This bit selects between the two operating conversion modes (direct
or auto) when the Internal trigger is active. This bit is always cleared to '0' (direct-mode) when an
external trigger is active.
CMODE = 0: Direct-mode. The analog inputs from [SA3:SA0] to [EA3:EA0] are converted
sequentially (see Table 12) one time, [SA3:SA0] first and [EA3;EA0] last. When one set of
conversions is complete, the ADC is idle and waits for a new trigger. The external trigger is
restricted to this mode of operation only.
CMODE = 1: Auto-mode. The analog inputs from [SA3:SA0] to [EA3:EA0] are converted
sequentially (see Table 12) and repeatedly, [SA3:SA0] first and [EA3;EA0] last. When one set of
conversions is complete, the ADC multiplexer returns to the starting address [SA3:SA0] and
repeats the process. Repetitive conversions continue until auto-mode is halted by rewriting the
ADC Control Register to direct-mode, or until the external trigger is enabled. Auto-mode works
only for the internal trigger.
The channel address of the first analog input to be converted (see Table 12).
The channel address of the last analog input to be converted (see Table 12).
The number of channels selected for conversion may range from one to nine. Channels in the selected range
[SA3:SA0] to [EA3:EA0] are addressed sequentially according to the map shown in Table 12. If the ending
channel address [EA3:EA0] is less than or equal to the starting address [SA3:SA0], then only channel [SA3:SA0]
is converted. After power-on or reset, the ADC Control Register is cleared (0x0000).
Channel CH8 is used for chip temperature measurement via the on-chip temperature sensor. It is not for external
analog input (see the On-chip Temperature Sensor section for details).
SA3/EA3
0
0
0
0
0
0
0
0
1
Table 12. Analog Input Channel Address Map
SA2/EA2
0
0
0
0
1
1
1
1
0
SA1/EA1
0
0
1
1
0
0
1
1
0
SA0/EA0
0
1
0
1
0
1
0
1
0
ANALOG INPUT
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7
CH8
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