Table 90. Boundary-scan Signals for the Analog Comparator
Signal
Name
Direction as Seen from
the Comparator
Recommended Input
when Not in Use
Output Values when
Recommended Inputs are Used
Description
AC_IDLE
Input
Output
Input
Input
Turns off Analog
comparator when true
1
Depends upon µC code being
executed
ACO
Analog Comparator
Output
Will become input to µC
code being executed
0
ACME
ACBG
Uses output signal from
ADC mux when true
0
Depends upon µC code being
executed
Bandgap Reference
enable
0
Depends upon µC code being
executed
Scanning the ADC
Figure 123 shows a block diagram of the ADC with all relevant control and observe signals. The Boundary-scan cell from
Figure 122 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 123. Analog to Digital Converter
VCCREN
AREF
IREFEN
2.56V
ref
To Comparator
PASSEN
MUXEN_7
ADC_7
MUXEN_6
ADC_6
MUXEN_5
ADC_5
MUXEN_4
ADC_4
ADCBGEN
SCTEST
1.22V
ref
EXTCH
MUXEN_3
ADC_3
PRECH
PRECH
AREF
AREF
DACOUT
COMP
MUXEN_2
ADC_2
MUXEN_1
ADC_1
MUXEN_0
ADC_0
DAC_9..0
ADCEN
10-bit DAC
+
-
G10
G20
ACTEN
GNDEN
+
+
NEGSEL_2
NEGSEL_1
NEGSEL_0
10x
-
20x
-
HOLD
ADC_2
ADC_1
ST
ACLK
AMPEN
ADC_0
The signals are described briefly in Table 91.
234
ATmega32(L)
2503J–AVR–10/06
ATMEL [ ATMEL ]
