Rainbow Electronics ATmega32L - Manual (Page 232)

232
ATmega32(L)
2503C–AVR–10/02
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
The signals are described briefly in Table 92.
Table 91. 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
+
-
+
-
10x 20x
G10 G20
ST
ACLK
AMPEN
2.56V
ref
IREFEN
AREF
VCCREN
DAC_9..0
ADCEN
HOLD
PRECH
GNDEN
PASSEN
ACTEN
COMP
SCTEST
ADCBGEN
To Comparator
1.22V
ref AREF