Datasheet

AMC7823
www.ti.com SLAS453F –APRIL 2005–REVISED MARCH 2012
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 Bit 0
MSB 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 LSB
CMOD X X X SA3 SA2 SA1 SA0 EA3 EA2 EA1 EA0 X X X X
E
X : Don't Care
CMODE 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.
SA3–SA0 The channel address of the first analog input to be converted (see Table 12).
EA3–EA0 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 eight. Channels in the selected range
[SA3:SA0] to [EA3:EA0] are addressed sequentially according to the map shown in Table 12. The starting
address [SA3:SA0] must not be greater than the ending address [EA:3:EA0]. When the internal trigger is
selected, the staring address must be '0000' (that is, CH-0); otherwise, the ADC conversion may not be correct.
Table 13 shows the allowed range of analog input channels for each ADC conversion mode. 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).
Table 12. Analog Input Channel Address Map
SA3/EA3 SA2/EA2 SA1/EA1 SA0/EA0 ANALOG INPUT
0 0 0 0 CH0
0 0 0 1 CH1
0 0 1 0 CH2
0 0 1 1 CH3
0 1 0 0 CH4
0 1 0 1 CH5
0 1 1 0 CH6
0 1 1 1 CH7
1 0 0 0 CH8
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