ata6616 ATMEL Corporation, ata6616 Datasheet - Page 229

• Manufacturer Part Number: ata6616
• Description: Microcontroller With Lin Transceiver, 5v Regulator And Watchdog
• Manufacturer: ATMEL Corporation

4.18.10
4.18.11
4.18.11.1
9132A–AUTO–10/08
DRAFT
Internal Voltage Reference Output
Register Description
ADMUX – ADC Multiplexer Selection Register
The internal voltage reference is output on XREF pin as described in
turned on (see
77). Addition of an external filter capacitor (5 - 10 nF) on XREF pin may be necessary.
XREF pin can be coupled to an analog input of the ADC.
Table 4-56.
Notes:
• Bit 7:6 – REFS1:REFS0: Voltage Reference Selection Bits
These bits and AREFEN bit from the Analog Miscellaneous Control Register (AMISCR) select
the voltage reference for the ADC, as shown in
conversion, the change will not go in effect until this conversion is complete (ADIF in ADCSRA
register is set). Whenever these bits are changed, the next conversion will take 25 ADC clock
cycles. If active channels are used, using AVCC or an external AREF higher than (AVcc - 1V) is
not recommended, as this will affect ADC accuracy. The internal voltage reference options may
not be used if an external voltage is being applied to the AREF pin.
Table 4-57.
Bit
Read/Write
Initial Value
XREFEN
REFS1
X
X
0
1
1
1
0
(2)
(1)
1.
2.
3. In these configurations, the pin pull-up must be turned off and the pin digital output must be set
4. Vcc in range 4.5 - 5.5V.
(1)
See ”Bit 1 – XREFEN: Internal Voltage Reference Output Enable” on page 235.
See ”Bit 7:6 – REFS1:REFS0: Voltage Reference Selection Bits” on page 229.
in Hi-Z.
REFS0
Internal Voltage Reference Output
Voltage Reference Selections for ADC
REFS1
Section 4.7.2.1 “Voltage Reference Enable Signals and Start-up Time” on page
REFS1
R/W
0
0
1
1
7
0
x
0
1
(2)
REFS0
AREFEN Voltage Reference (V
R/W
6
0
0
1
0
0
REFS0
1
1
x
ADLAR
ATA6616/ATA6617 [Preliminary]
R/W
AVcc used as Voltage Reference, disconnected from AREF pin.
External Voltage Reference at AREF pin (AREF
Internal 1.1V Voltage Reference.
Internal 2.56V Voltage Reference.
(3)
5
0
Voltage Reference Output (I
Hi-Z, the pin can be used as AREF input or other alternate
functions.
XREF = 1.1V
XREF = 2.56V
MUX4
R/W
4
0
Table
(3)
(3)(4)
MUX3
R/W
3
0
REF
4-57. If these bits are changed during a
) Selection
MUX2
R/W
2
0
load
100 µA)
MUX1
R/W
Table 4-56
1
0
MUX0
R/W
2.0V)
0
0
if the ADC is
ADMUX
229