101-0577 Rabbit Semiconductor, 101-0577 Datasheet - Page 29

• Manufacturer Part Number: 101-0577
• Description: KIT DEV FOR BL2500 COYOTE
• Manufacturer: Rabbit Semiconductor
• Series: Coyoter
• Type: Single Board Computers (SBC)r

Specifications of 101-0577

• Contents: SBC, Dev. Board, AC Adapter, Cable and Dynamic C® CD-ROM
• Product: Modules
• Data Bus Width: 10 bit
• Processor Type: Rabbit 3000
• Sram: 128 KB
• Flash: 256 KB
• Number Of I/os: 24
• Backup Battery: 3 V Lithium Coin Type
• Operating Voltage: 8 V to 40 V
• Power Consumption: 1 W
• Board Size: 100 mm x 100 mm x 29 mm
• Description/function: Computer Module
• Interface Type: Ethernet
• For Use With/related Products: BL2510
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

3.4 Analog Features
3.4.1 A/D Converter
The A/D converter, shown in Figure 13, compares the DA0 voltage to AD0, the voltage
presented to the A/D converter. DA0 therefore cannot be used for the D/A converter when
the A/D converter is being used.
The A/D converter programs DA0 using a successive-approximation binary search until
DA0 equals the A/D converter input voltage. That programmed DA0 voltage is then
reported as the A/D converter value.
The A/D converter transforms the voltage at DA0 into a 13.2 mV window around DA0.
Because the A/D converter circuit uses a 13.2 mV window, the accuracy is ±6.6 mV. DA0
can range from 0.1 V to 3.1 V, which represents 227 steps of 13.2 mV. This represents an
accuracy of approximately 8 bits. Since the D/A converter is able to change the DA0 out-
put in 3.22 mV steps, there are 930 steps over the range from 0.1 V to 3.1 V. This repre-
sents a resolution of more than 9 bits.
For example, if DA0 is 1.650 V, the window in the A/D converter would be 1.643 V to
1.657 V. If AD0 > 1.657 V, PB2 would read high and PB3 would read low. If 1.643 V <
AD0 < 1.657 V, PB2 would read low and PB3 would read low. This is the case when the
A/D input is exactly the same as DA0. If AD0 < 1.643 V, PB2 would read low and PB3
would read high. The A/D converter input, AD0, is the same as DA0 only when both PB2
and PB3 are low.
PB3 can be imagined to be a “DA0 voltage is too high” indicator. If DA0 is larger than the
analog voltage presented at AD0, then PB3 will be true (high). If this happens, the pro-
gram will need to reduce the DA0 voltage.
User’s Manual
Figure 13. Schematic Diagram of A/D Converter
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