Rainbow-electronics ATmega8515L Manuel d'utilisateur télécharger pdf (Page 160)

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ATmega8515(L)

2512A–AVR–04/02

Analog Comparator TheAnalog Comparatorcompares theinput values on the positive pin AIN0and nega-

tive pin AIN1. When thevoltage on the positive pin AIN0ishigher than thevoltage on

the negative pin AIN1, theAnalog ComparatorOutput, ACO, isset. The comparator’s

output can be set to trigger theTimer/Counter1 Input Capture function. Inaddition, the

comparatorcan trigger a separate interrupt, exclusive to theAnalog Comparator.The

usercan select Interrupttriggering on comparator output rise,fall or toggle. A block dia-

gram of the comparator and itssurrounding logic isshowninFigure 70.

Figure 70. Analog ComparatorBlock Diagram

(1)

Note: 1. Refer to Figure1onpage 2 and Table29 on page 64 for Analog Comparatorpin

placement.

Analog Comparator Control

and Status Register – ACSR

• Bit 7 – ACD: Analog Comparator Disable

When thisbit iswritten a logic one, the power to theAnalog Comparator isswitched off.

Thisbit can be set at any time to turnoff theAnalog Comparator.Thiswill reduce power

consumption in Active andIdlemode. When changing theACD bit, theAnalog Compar-

atorInterruptmust be disabledbyclearing theACIE bit in ACSR. Otherwiseaninterrupt

can occurwhen the bit ischanged.

• Bit 6 – ACBG: Analog Comparator Bandgap Select

When thisbit isset, a fixedbandgapreferencevoltage replaces the positive input to the

Analog Comparator. When thisbit iscleared, AIN0is applied to the positive input of the

Analog Comparator. See “Internal Voltage Reference” on page 47.

• Bit 5 – ACO: Analog Comparator Output

Theoutput of theAnalog Comparator issynchronized and then directly connected to

ACO.The synchronization introduces a delay of 1 - 2 clock cycles.

• Bit 4 – ACI: Analog Comparator Interrupt Flag

Thisbit isset by hardware when a comparator output event triggers theinterruptmode

definedbyACIS1and ACIS0. TheAnalog ComparatorInterrupt routine is executed if

ACBG

BANDGAP

REFERENCE

Bit 76543 210

ACD ACBG ACO ACI ACIE ACIC ACIS1 ACIS0 ACSR

Read/Write R/W R/W RR/W R/W R/W R/W R/W

Initial Value 0 0 N/A00000

1 2 ... 155 156 157 158 159 160 161 162 163 164 165 ... 222 223

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Rainbow-electronics ATmega8515L Manuel d'utilisateur Page 160