XC886/888CLM
Analog-to-Digital Converter
User’s Manual
16-13
V1.3, 2010-02
ADC, V 1.0
16.4.4.2
Request Source Control
If the conversion requested by the source is not related to an external trigger event
(EXTR = 0), the valid bit V = 1 directly requests the conversion by setting signals
REQPND and REQCHNRV to 1. In this case, no conversion will be requested if V = 0.
A gating mechanism allows the user to enable/disable conversion requests according to
bit ENGT.
Figure 16-6
Sequential Request Source Control
If the requested conversion is sensitive to an external trigger event (EXTR = 1), the
signal REQTR can be taken into account (with ENTR = 1) or the software can write
TREV = 1. Both actions set the event flag EV. The event flag EV = 1 indicates that an
external event has taken place and a conversion can be requested (EV can be set only
if a conversion request is valid with V = 1). In this case, the signal REQCHNRV is derived
from bit EV.
In the queue backup register, bit EXTR is always considered as 0. If a queue controlled
conversion has been started and aborted due to a higher priority conversion, the aborted
conversion will be restarted without waiting for a new trigger event.
ADC_seq_reqsrc_control
REQPND
REQCHNRV
set
reset
EV
AND
0
1
OR
AND
ENTR
REQTR
TREV
OR
CEV
conversion
started
ENGT
rh
w
w
rw
rw
V
1 0
EXTR
rh
1
0
*
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