Rainbow Electronics ATmega128L - Manual (Page 218)

218
ATmega128(L)
2467B–09/01
Analog Comparator
The analog comparator compares the input values on the positive pin AIN0 and nega-
tive pin AIN1. When the voltage on the positive pin AIN0 is higher than the voltage on
the negative pin AIN1, the Analog Comparator Output, ACO, is set. The comparator’s
output can be set to trigger the Timer/Counter1 Input Capture function. In addition, the
comparator can trigger a separate interrupt, exclusive to the Analog Comparator. The
user can select Interrupt triggering on comparator output rise, fall or toggle. A block dia-
gram of the comparator and its surrounding logic is shown in
Figure 106.
Figure 106. Analog Comparator Block Diagram
Notes: 1. See Table 93 on page 220.
2. Refer to Figure 1 on page 2 and Table 30 on page 69 for Analog Comparator pin
placement.
Special Function IO Register –
SFIOR
• Bit 3 - ACME: Analog Comparator Multiplexer Enable
When this bit is written logic one and the ADC is switched off (ADEN in ADCSRA is
zero), the ADC multiplexer selects the negative input to the Analog Comparator. When
this bit is written logic zero, AIN1 is applied to the negative input of the Analog Compar-
ator. For a detailed description of this bit, see
“Analog Comparator Multiplexed Input” on
page 220.
Analog Comparator Control
and Status Register – ACSR
ACBG
BANDGAP
REFERENCE
ADC MULTIPLEXER
OUTPUT
ACME
ADEN
1)
Bit 7 6 5 4 3 2 1 0
TSM – – ADHSM ACME PUD PSR2 PSR10 SFIOR
Read/Write R/W R R R/W R/W R/W R/W R/W
Initial value 0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
ACD ACBG ACO ACI ACIE ACIC ACIS1 ACIS0 ACSR
Read/Write R/W R/W R R/W R/W R/W R/W R/W
Initial value 0 0 N/A 0 0 0 0 0