Rainbow-electronics AT90LS4433 Manual do Utilizador descarregar pdf (Página 68)

AT90S/LS4433

1042G–AVR–09/02

ADC Multiplexer Select

• Bit 7 – Res: Reserved Bit

This bit is a reserved bit in the AT90S4433, and should be written to zero if accessed.

• Bit 6 – ADCBG: ADC Bandgap Select

When this bit is set and the BOD is enabled (BODEN Fuse is programmed), a fixed

bandgap voltage of 1.22V ± 0.1V replaces the normal input to the ADC. When this bit is

cleared, the normal input pin (as selected by MUX2..MUX0) is applied to the ADC.

• Bits 5..3 – Res: Reserved Bits

These bits are reserved bits in the AT90S4433, and should be written to zero if

accessed.

• Bits 2..0 – MUX2..MUX0: Analog Channel Select Bits 2 - 0

The value of these three bits selects which analog input 5 - 0 is connected to the ADC.

ADC Control and Status

‘

• Bit 7 – ADEN: ADC Enable

Writing a logical “1” to this bit enables the ADC. By clearing this bit to zero, the ADC is

turned off. Turning the ADC off while a conversion is in progress will terminate this

conversion.

• Bit 6 – ADSC: ADC Start Conversion

In Single Conversion mode, a logical “1” must be written to this bit to start each conver-

sion. In Free Run mode, a logical “1” must be written to this bit to start the first

conversion. The first time ADSC has been written after the ADC has been enabled, or if

ADSC is written at the same time as the ADC is enabled, a dummy conversion will pre-

cede the initiated conversion. This dummy conversion performs initialization of the ADC.

ADSC remains high during the conversion. ADSC goes low after the conversion is com-

plete, but before the result is written to the ADC Data Registers. This allows a new

conversion to be initiated before the current conversion is complete. The new conver-

sion will then start immediately after the current conversion completes. When a dummy

conversion precedes a real conversion, ADSC will stay high until the real conversion

completes.

Writing a “0” to this bit has no effect.

Bit 76543210

$07 ($27) – ADCBG –––MUX2 MUX1 MUX0 ADMUX

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

InitialValue00000000

Bit 76543210

$06 ($26) ADEN ADSC ADFR ADIF ADIE ADPS2 ADPS1 ADPS0 ADCSR

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

InitialValue00000000

1 2 ... 63 64 65 66 67 68 69 70 71 72 73 ... 124 125

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