Hardware Reference
In-Depth Information
An external triggering function allows the user to synchronize the ATD conversion process
with external events. The ATD module can be configured to trigger on edges or levels of different
polarities. Several bits in the ATD
x
CTL2 register are used to configure this function. The ex-
ternal triggering capability allows the user to start an A/D conversion when it is desired. The
external trigger source is AN7 for AD0 and AN15 for AD1. Connecting the trigger channels
together on MCUs with two ATDs allows synchronized conversions on the two converters.
Examples of the trigger source could be external logic, software driving an output pin, a timer
output-compare output pin, or a PWM channel.
Conversion results can be signed or unsigned. Signed data is represented as two's comple-
ment. The ATD
x
CTL5 register controls this function. A signed conversion sequence treats the
value (
V
RH
2
V
RL
)/2 as zero reference. Input signals greater than this value produce positive
results; input signals lower than this value result in negative results.
The ATD module has three operation modes: power-down mode, idle mode, and run mode.
P
OWER
-D
OWN
M
ODE
The ATD module can be powered down to save power consumption in one of three ways.
1. By clearing the ADPU bit of the ATD
x
CTL2 register
2. By executing the stop instruction
3. By executing the wai instruction with the AWAI bit of the ATD
x
CTL2 register
set to 1
The ATD module is in power-down mode out of reset. Once the command to power
down has been received, the ATD module aborts any conversion sequence in progress and
enters power-down mode. When the module is powered up again, the module requires a
recovery time of about 20
s to stabilize the bias settings in the analog electronics before
conversions can be performed. Powering the module up and down does not change the con-
tents of the register file, and in power-down mode, the control and result registers are still
accessible.
μ
I
DLE
M
ODE
Idle mode for the ATD module is defined as the state in which the ATD module is powered
up and ready to perform A/D conversion, but is not actually performing a conversion at the
present time. Access to all control, status, and result registers is available. The module is con-
suming near the maximum power.
R
UN
M
ODE
The run mode for the ATD module is defined as the state in which the ATD module is pow-
ered up and currently performing an A/D conversion. Complete access to all control, status,
and result registers is available. The module consumes the maximum power.
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