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R01UH0336EJ0102 Rev.1.02
Page 1285 of 1538
Jul 17, 2014
V850E2/PG4-L
Section 23 A/D Converter
23.3.5
Starting A/D Conversion (Start Triggers)
A/D conversion can be started by a software or hardware trigger which is
specified in ADCAnCTL1.ADCAnMD1.
When an A/D conversion is triggered for multiple CGs, the conversion order
depends on the priorities of the CGs (see Section 23.3.3 (1), Order of A/D
Conversion).
Note 1.
The ADCAn ignores triggers for CGi if there is no channel assigned to the CGi
(ADCAnCGi = 0000 0000
H
).
Note 2.
In one-shot conversion mode, the A/D converter stores one start trigger.
If start triggers are set for CGi before the previously triggered A/D
conversion of the CGi is completed, the first additional start trigger causes
another A/D conversion to be performed immediately after the current CGi
A/D conversion, but all the other additional start triggers of the same CGi
are ignored (see Figure 23-6, Operation When Start Trigger is Input Before
Completion of Conversion).
Note 3.
In continuous conversion mode, additional start triggers that are generated
before a stop trigger is generated are ignored.
(1)
Software Start Trigger
The A/D conversion of CGi is triggered by setting ADCAnTRGi.ADCAnSTTi to
1, if the A/D converter is enabled (ADCAnCTL0.ADCAnCE = 1).
Example
of software
start trigger
timing
The following figure shows the timing of a software start trigger under the
following conditions:
• ADCAnTCLK clock = PCLK/2 (ADCAnCTL1.ADCAnFR[1:0] = 01
B
)
Figure 23-9
Example of Software Start Trigger Timing
1. Software trigger for CGi is written.
2. A/D conversion starts at the next falling edge of ADCAnTCLK.
The status signal ADCAnCNVi becomes active and the status bit
ADCAnSTR2.ADCAnSTi is set to indicate that A/D conversion of CGi is
running.
PCLK
ADCAnTCLK
Status
Idle
Conversion of CGi
ADCAnTRGi.ADCAnSTTi
ADCAnSTR2.ADCAnSTi
(1)
(2)
ADCAnCNVi signal