Datasheet

251
ATmega329/3290/649/6490
2552I–AVR–04/07
Scanning the ADC Figure 116 shows a block diagram of the ADC with all relevant control and observe sig-
nals. The Boundary-scan cell from Figure 112 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 116. Analog to Digital Converter
The signals are described briefly in Table 111.
Table 110. 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