AT90S/LS4434 and AT90S/LS8535
69
Notes:
1. Minimum for AV
CC
is 2.7V.
2. Maximum for AV
CC
is 6.0V.
I/O Ports
All AVR ports have true read-modify-write functionality when used as general digital I/O ports. This means that the direction
of one port pin can be changed without unintentionally changing the direction of any other pin with the SBI and CBI instruc-
tions. The same applies for changing drive value (if configured as output) or enabling/disabling of pull-up resistors (if
configured as input).
Port A
Port A is an 8-bit bi-directional I/O port.
Three I/O memory address locations are allocated for Port A, one each for the Data Register – PORTA, $1B($3B), Data
Direction Register – DDRA, $1A($3A) and the Port A Input Pins – PINA, $19($39). The Port A Input Pins address is read-
only, while the Data Register and the Data Direction Register are read/write.
All port pins have individually selectable pull-up resistors. The Port A output buffers can sink 20 mA and thus drive LED dis-
plays directly. When pins PA0 to PA7 are used as inputs and are externally pulled low, they will source current if the
internal pull-up resistors are activated.
Port A has an alternate function as analog inputs for the ADC. If some Port A pins are configured as outputs, it is essential
that these do not switch when a conversion is in progress. This might corrupt the result of the conversion.
During Power-down Mode, the Schmitt trigger of the digital input is disconnected. This allows analog signals that are close
to V
CC
/2 to be present during power-down without causing excessive power consumption.
ADC Characteristics
T
A
= -40
°
C to 85
°
C
Symbol
Parameter
Condition
Min
Typ
Max
Units
Resolution
10
Bits
Absolute accuracy
VREF = 4V
ADC clock = 200 kHz
1
2
LSB
Absolute accuracy
VREF = 4V
ADC clock = 1 MHz
4
LSB
Absolute accuracy
VREF = 4V
ADC clock = 2 MHz
16
LSB
Integral Non-linearity
V
REF
> 2V
0.5
LSB
Differential Non-linearity
V
REF
> 2V
0.5
LSB
Zero Error (Offset)
1
LSB
Conversion Time
65
260
µ
s
Clock Frequency
50
200
kHz
AV
CC
Analog Supply Voltage
V
CC
- 0.3
V
CC
+ 0.3
V
V
REF
Reference Voltage
2
AV
CC
V
R
REF
Reference Input Resistance
6
10
13
k
Ω
V
IN
Input Voltage
AGND
AREF
V
R
AIN
Analog Input Resistance
100
M
Ω