Rainbow Electronics ATmega128L - Manual (Page 253)

253
ATmega128(L)
2467B–09/01
Scanning the ADC Figure 130 shows a block diagram of the ADC with all relevant control and observe sig-
nals. The Boundary-scan cell from
Figure 126 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 130. Analog to Digital Converter
The signals are described briefly in Table 104.
Table 103. 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
ADHSM
ADHSM