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ADuC836
–18–
ADCMODE (ADC Mode Register)
Used to control the operational mode of both ADCs.
SFR Address D1H
Power-On Default Value 00H
Bit Addressable No
Table V. ADCMODE SFR Bit Designations
Bit Name Description
7 ––– Reserved for Future Use
6 ––– Reserved for Future Use
5 ADC0EN Primary ADC Enable.
Set by the user to enable the primary ADC and place it in the mode selected in MD2–MD0, below.
Cleared by the user to place the primary ADC in power-down mode.
4 ADC1EN Auxiliary ADC Enable.
Set by the user to enable the auxiliary ADC and place it in the mode selected in MD2–MD0, below.
Cleared by the user to place the auxiliary ADC in power-down mode.
3 ––– Reserved for Future Use
2 MD2 Primary and Auxiliary ADC Mode bits.
1 MD1 These bits select the operational mode of the enabled ADC as follows:
0 MD0 MD2
MD1
MD0
0
0
0
ADC Power-Down Mode (Power-On Default)
0
0
1
Idle Mode. The ADC filter and modulator are held in a reset state although the
modulator clocks are still provided.
0
1
0
Single Conversion Mode. A single conversion is performed on the enabled ADC.
On completion of the conversion, the ADC data registers (ADC0H/M and/or ADC1H/L)
are updated, the relevant flags in the ADCSTAT SFR are written, and power-down is
re-entered with the MD2–MD0 accordingly being written to 000.
0
1
1
Continuous Conversion. The ADC data registers are regularly updated at the selected
update rate (see SF Register).
1
0
0
Internal Zero-Scale Calibration. Internal short automatically connected to the enabled
ADC input(s).
1
0
1
Internal Full-Scale Calibration. Internal or external V
REF
(as determined by XREF0
and XREF1 bits in ADC0/1CON) is automatically connected to the enabled ADC
input(s) for this calibration.
1
1
0
System Zero-Scale Calibration. User should connect system zero-scale input to the
enabled ADC input(s) as selected by CH1/CH0 and ACH1/ACH0 bits in the
ADC0/1CON Register.
1
1
1
System Full-Scale Calibration. User should connect system full-scale input to the
enabled ADC input(s) as selected by the CH1/CH0 and ACH1/ACH0 bits in the
ADC0/1CON Register.
NOTES
1. Any change to the MD bits will immediately reset both ADCs. A write to the MD2–0 bits with no change is also treated as a reset. (See exception to this in Note 3.)
2. If ADC0CON is written when ADC0EN = 1, or if ADC0EN is changed from 0 to 1, then both ADCs are also immediately reset. In other words, the primary ADC is
given priority over the auxiliary ADC, and any change requested on the primary ADC is immediately responded to.
3. On the other hand, if ADC1CON is written or if ADC1EN is changed from 0 to 1, only the auxiliary ADC is reset. For example, if the primary ADC is continuously converting
when the auxiliary ADC change or enable occurs, the primary ADC continues undisturbed. Rather than allow the auxiliary ADC to operate with a phase difference from
the primary ADC, the auxiliary ADC will fall into step with the outputs of the primary ADC. The result is that the first conversion time for the auxiliary ADC will be
delayed up to three outputs while the auxiliary ADC update rate is synchronized to the primary ADC.
4. Once ADCMODE has been written with a calibration mode, the RDY0/1 bits (ADCSTAT) are immediately reset and the calibration commences. On completion, the appropriate
calibration registers are written, the relevant bits in ADCSTAT are written, and the MD2–0 bits are reset to 000 to indicate the ADC is back in Power-Down mode.
5. Any calibration request of the auxiliary ADC while the temperature sensor is selected will fail to complete. Although the RDY1 bit will be set at the end of the calibration
cycle, no update of the calibration SFRs will take place and the ERR1 bit will be set.
6. Calibrations are performed at maximum SF (see SF SFR) value, guaranteeing optimum calibration operation.
REV. A