101-0577 Rabbit Semiconductor, 101-0577 Datasheet - Page 30

• 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

PB2 can be imagined to be a “DA0 voltage is too low” indicator. If DA0 is smaller than
the analog voltage presented at AD0, then PB2 will be true (high). If this happens, the pro-
gram will need to raise the DA0 voltage.
The A/D converter has no reference voltage. There is a relative accuracy between mea-
surements, but no absolute accuracy without calibration. This is because the +3.3 V supply
can vary ±5%, the pulse-width modulated outputs might not reach the full 0 V and 3.3 V
rails out of the Rabbit 3000 microprocessor, and the gain resistors used in the circuit have
a 1% tolerance. For these reasons, each Coyote needs to be calibrated individually, with
the constants held in software, to be able to rely on an absolute accuracy. The Coyote has
this calibration support.
An A/D conversion takes less than 100 ms with a 29.4 MHz Coyote.
3.4.2 D/A Converters
Two D/A converter outputs, DA0 and DA1, are supplied on the Coyote. These are shown
in Figure 14.
The D/A converters have no reference voltage. Although they may be fairly accurate from
one programmed voltage to the next, they do not have absolute accuracy. This is because
the +3.3 V supply can change ±5%, the PWM outputs might not achieve the full 0 V and 3.3 V
rail out of the processor, and the gain resistors in the circuit have a 1% tolerance. The D/A
converters therefore need individual calibration, with the calibration constants held in
software before absolute accuracy can be relied on. The Coyote has such calibration.
Note that DA0 is used to provide a reference voltage for the A/D converter and is unavail-
able for D/A conversion when the A/D converter is being used.
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Figure 14. Schematic Diagram of D/A Converters
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Coyote (BL2500)