Silicon Laboratories C8051F342 ADC Window Compare Example Right-Justified Differential Data

C8051F340/1/2/3/4/5/6/7

5.4.2. Window Detector In Differential Mode

Figure 5.8 shows two example window comparisons for right-justified, differential data, with ADC0LTH:ADC0LTL = 0x0040 (+64d) and ADC0GTH:ADC0GTH = 0xFFFF (-1d). In differential mode, the measurable voltage between the input pins is between -VREF and VREF*(511/512). Output codes are rep- resented as 10-bit 2’s complement signed integers. In the left example, an AD0WINT interrupt will be gen- erated if the ADC0 conversion word (ADC0H:ADC0L) is within the range defined by ADC0GTH:ADC0GTL and ADC0LTH:ADC0LTL (if 0xFFFF (-1d) < ADC0H:ADC0L < 0x0040 (64d)). In the right example, an AD0WINT interrupt will be generated if the ADC0 conversion word is outside of the range defined by the ADC0GT and ADC0LT registers (if ADC0H:ADC0L < 0xFFFF (-1d) or ADC0H:ADC0L > 0x0040 (+64d)). Figure 5.9 shows an example using left-justified data with equivalent ADC0GT and ADC0LT register set- tings.

ADC0H:ADC0L

Input Voltage

(Px.x - Px.x)

ADC0H:ADC0L

Input Voltage

(Px.x - Px.x)

VREF x (511/512)

VREF x (64/512)

VREF x (-1/512)

-VREF

0x01FF

0x0041

0x0040

0x003F

0x0000

0xFFFF

0xFFFE

0x0200

	VREF x (511/512)	0x01FF
AD0WINT
not affected
		0x0041
ADC0LTH:ADC0LTL	VREF x (64/512)	0x0040
AD0WINT=1		0x003F
		0x0000
ADC0GTH:ADC0GTL	VREF x (-1/512)	0xFFFF
		0xFFFE
AD0WINT
not affected
	-VREF	0x0200

AD0WINT=1

ADC0GTH:ADC0GTL

AD0WINT

not affected

ADC0LTH:ADC0LTL

AD0WINT=1

Figure 5.8. ADC Window Compare Example: Right-Justified Differential Data

ADC0H:ADC0L

Input Voltage

(Px.x - Px.x)

ADC0H:ADC0L

Input Voltage

(Px.x - Px.y)

VREF x (511/512)

VREF x (64/512)

VREF x (-1/512)

-VREF

0x7FC0

0x1040

0x1000

0x0FC0

0x0000

0xFFC0

0xFF80

0x8000

	VREF x (511/512)	0x7FC0
AD0WINT
not affected
		0x1040
ADC0LTH:ADC0LTL	VREF x (64/512)	0x1000
AD0WINT=1		0x0FC0
		0x0000
ADC0GTH:ADC0GTL	VREF x (-1/512)	0xFFC0
		0xFF80
AD0WINT
not affected
	-VREF	0x8000

AD0WINT=1

ADC0GTH:ADC0GTL

AD0WINT

not affected

ADC0LTH:ADC0LTL

AD0WINT=1

Figure 5.9. ADC Window Compare Example: Left-Justified Differential Data

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