28128 Parallax Inc, 28128 Datasheet - Page 54

• Manufacturer Part Number: 28128
• Description: KIT BASIC ANALOG/DIGI PARTS ONLY
• Manufacturer: Parallax Inc

Specifications of 28128

• Accessory Type: ADC, DAC
• Product: Microcontroller Accessories
• For Use With/related Products: BASIC Stamp® 2 and Board of Education
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

measured voltage in decimal form (our DVM output). The BASIC Stamp must also be
programmed to send binary control signals to make the ADC0831 do its job.
Figure 3-2 shows a pin map of the ADC0831. Each pin has a number and a label. The
number is important for getting the wires connected to the right pins when constructing
your circuit. The labels indicate the function of each pin.
The notation for the ADC0831's inputs and outputs works as follows: Vin(+) is the
analog input, and D0 is the serial output. VREF and Vin(-) are used to bias the IC. Vcc
and GND are used for supplying power to the IC. Vcc is essentially the same term as Vdd
on the Board of Education, and GND corresponds to Vss. /CS stands for active low chip
select, and CLK stands for clock. Both are inputs for binary control signals.
To prime the ADC0831 for taking a measurement, the /CS pin has to receive a signal
from the BASIC Stamp that starts high, then goes low. This signal has to stay low for the
duration of the conversion. Then the CLK input must receive a single clock pulse (a term
introduced in Chapter #2, Figure 2-8) to signify that the conversion should start at the
next clock pulse. For this IC, a clock pulse starts low, goes high, then goes low again. It
takes 8 more clock pulses to complete the conversion. Each time a clock pulse is received
by the CLK input, another of the serial bits is sent by the D0 output.
1
7
6
Vdd
/CS
CLK
D0
ADC0831
8
Vref
5
Vin(+)
Binary control signal: A voltage signal with two possible states, low or high, that is sent to
tell a device how or when to do something. The ADC0831 requires control signals to activate
it and a clock signal to synchronize the sending of each of the it's output bits.
Bias: A method of applying specific voltage levels at certain places in a circuit to calibrate or
tune it.
GND
Vin(-)
2
4
3
2
3
4
1
ADC0831
/CS
Vin (+)
Vin (-)
GND
CLK
Vref
Vcc
D0
8
7
6
5
Figure 3-2
ADC0831 Circuit Symbol and Pin Map.
The pin map on the right shows the pins and
labels according to where they are on the chip.
The circuit symbol on the left also shows the
pins and their labels, but it's typically drawn in a
way that most conveniently fits into the
schematic.