C8051F360 datasheet(48/288 Pages) SILABS

48 / 288 page

C8051F360/1/2/3/4/5/6/7/8/9

Rev. 1.0

5.1.

Analog Multiplexer

AMUX0 selects the positive and negative inputs to the ADC. Any of the following may be selected as the

positive input: the AMUX0 Port I/O inputs, the on-chip temperature sensor, or the positive power supply

(VDD). Any of the following may be selected as the negative input: the AMUX0 Port I/O inputs, VREF, or

GND. When GND is selected as the negative input, ADC0 operates in Single-ended Mode; all other

times, ADC0 operates in Differential Mode. The ADC0 input channels are selected in the AMX0P and

AMX0N registers as described in SFR Definition 5.1 and SFR Definition 5.2.

The conversion code format differs between Single-ended and Differential modes. The registers ADC0H

and ADC0L contain the high and low bytes of the output conversion code from the ADC at the completion

of each conversion. Data can be right-justified or left-justified, depending on the setting of the AD0LJST bit

(ADC0CN.0). When in Single-ended Mode, conversion codes are represented as 10-bit unsigned integers.

Inputs are measured from ‘0’ to VREF * 1023/1024. Example codes are shown below for both right-justified

and left-justified data. Unused bits in the ADC0H and ADC0L registers are set to ‘0’.

When in Differential Mode, conversion codes are represented as 10-bit signed 2’s complement numbers.

Inputs are measured from -VREF to VREF * 511/512. Example codes are shown below for both right-justi-

fied and left-justified data. For right-justified data, the unused MSBs of ADC0H are a sign-extension of the

data word. For left-justified data, the unused LSBs in the ADC0L register are set to ‘0’.

Important Note About ADC0 Input Configuration: Port pins selected as ADC0 inputs should be config-

ured as analog inputs, and should be skipped by the Digital Crossbar. To configure a Port pin for analog

input, set to ‘0’ the corresponding bit in register PnMDIN (for n = 0,1,2,3). To force the Crossbar to skip a

Port pin, set to ‘1’ the corresponding bit in register PnSKIP (for n = 0,1,2,3). See Section “17. Port Input/

Output” on page 183 for more Port I/O configuration details.

Input Voltage

Right-Justified ADC0H:ADC0L

(AD0LJST = 0)

Left-Justified ADC0H:ADC0L

(AD0LJST = 1)

VREF x 1023/1024

0x03FF

0xFFC0

VREF x 512/1024

0x0200

0x8000

VREF x 256/1024

0x0100

0x4000

0x0000

Input Voltage

Right-Justified ADC0H:ADC0L

(AD0LJST = 0)

Left-Justified ADC0H:ADC0L

(AD0LJST = 1)

VREF x 511/512

0x01FF

0x7FC0

VREF x 256/512

0x0100

0x4000

0x0000

–VREF x 256/512

0xFF00

0xC000

–VREF

0xFE00

0x8000

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