Datasheet

262
8021G–AVR–03/11
ATmega329P/3290P
25.5.5 Scanning the ADC
Figure 25-8 shows a block diagram of the ADC with all relevant control and observe signals. The
Boundary-scan cell from Figure 25-4 is attached to each of these signals. The ADC need not be
used for pure connectivity testing, since all analog inputs are shared with a digital port pin as
well.
Figure 25-8. Analog to Digital Converter
The signals are described briefly in Table 25-4.
Table 25-3. Boundary-scan Signals for the Analog Comparator
Signal
Name
Direction as
Seen from the
Comparator Description
Recommended
Input when Not
in Use
Output Values when
Recommended Inputs
are Used
AC_IDLE input
Turns off Analog
Comparator when
true
1
Depends upon µC code
being executed
ACO output
Analog Comparator
Output
Will become input
to µC code being
executed
0
ACME input
Uses output signal
from ADC mux when
true
0
Depends upon µC code
being executed
ACBG input
Bandgap Reference
enable
0
Depends upon µC code
being executed
10-bit DAC +
-
AREF
PRECH
DACOUT
COMP
MUXEN_7
ADC_7
MUXEN_6
ADC_6
MUXEN_5
ADC_5
MUXEN_4
ADC_4
MUXEN_3
ADC_3
MUXEN_2
ADC_2
MUXEN_1
ADC_1
MUXEN_0
ADC_0
NEGSEL_2
ADC_2
NEGSEL_1
ADC_1
NEGSEL_0
ADC_0
EXTCH
+
-
1x
ST
ACLK
AMPEN
1.11V
ref
IREFEN
AREF
VCCREN
DAC_9..0
ADCEN
HOLD
PRECH
GNDEN
PASSEN
COMP
SCTEST
ADCBGEN
To Comparator
1.22V
ref
ACTEN
AREF