C8051F581-IMR Silicon Labs, C8051F581-IMR Datasheet - Page 61

• Manufacturer Part Number: C8051F581-IMR
• Description: 8-bit Microcontrollers - MCU 50MIPS 128kB 8kB SPI
• Manufacturer: Silicon Labs

Specifications of C8051F581-IMR

• Rohs: yes
• Core: 8051
• Processor Series: C8051
• Data Bus Width: 8 bit

For example, if ADC0GNH = 0xFC, ADC0GNL = 0x00, and GAINADD = 1, GAIN = 0xFC0 = 4032, and the
resulting equation is as follows:
The table below equates values in the ADC0GNH, ADC0GNL, and ADC0GNA registers to the equivalent
gain using this equation.
For any desired gain value, the GAIN registers can be calculated by the following:
Where:
GAIN is the 12-bit word of ADC0GNH[7:0] and ADC0GNL[7:4]
GAINADD is the value of the GAINADD bit (ADC0GNA.0)
gain is the equivalent gain value from 0 to 1.016
When calculating the value of GAIN to load into the ADC0GNH and ADC0GNL registers, the GAINADD bit
can be turned on or off to reach a value closer to the desired gain value.
For example, the initial example in this section requires a gain of 0.44 to convert 5 V full scale to 2.2 V full
scale. Using Equation 6.3:
If GAINADD is set to 1, this makes the equation:
The actual gain from setting GAINADD to 1 and ADC0GNH and ADC0GNL to 0x6CA is 0.4399. A similar
gain can be achieved if GAINADD is set to 0 with a different value for ADC0GNH and ADC0GNL.
ADC0GNH Value
Equation 6.3. Calculating the ADC0GNH and ADC0GNL Values from the Desired Gain
0xFC (default)
0xBC
0x7C
0x3C
0xFF
0xFF
GAIN
=
GAIN


0.44 1
ADC0GNL Value
0x00 (default)
GAIN
GAIN
–
=
0xF0
0xF0
0x00
0x00
0x00



4032
------------ -
4096


=
=
----- -
64
1






gain GAINADD
0.44 GAINADD




+

4096
1
–
–
GAINADD Value



1 (default)
----- -
64
Rev. 1.2
1
=


1
1
1
0
1
0.424 4096
=
0.984







----- -
64
----- -
64
1
1
+






0.016


GAIN Value

4032 + 64
1984 + 64
3008 + 64
4096 + 64

960 + 64
=
4095 + 0
C8051F58x/F59x
4096
4096
1738
=
1.0
=
0x06CA
Equivalent Gain
1.0 (default)
1.016
0.75
0.25
~1.0
0.5
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