AN1740 Freescale Semiconductor / Motorola, AN1740 Datasheet - Page 69

• Manufacturer Part Number: AN1740
• Description: Applications Using the Analog Subsystem on MC68HC05JJ/JP Series Microcontrollers
• Manufacturer: Freescale Semiconductor / Motorola

Using the A/D
Conversion Results
AN1740
MOTOROLA
can be terminated. This will make the sample start some time before the
A/D conversion start and end a short time after the A/D conversion start.
In mode 3, the OCF cannot be used easily to get a sample start before
the A/D conversion begins, since the OCF itself is the starting event. But,
the input to be sampled can be selected after the prior A/D conversion
ends (when the ICF is serviced) and then terminate the sample shortly
after the start of the A/D conversion when servicing the OCF.
Once a time count is determined for a given input signal, it can be
compared to a reference count for the full scale voltage, V
reference count for the lowest voltage, V
where:
This calculation also is shown as a flowchart for both absolute and
ratiometric values in
V
V
V
N
N
N
Freescale Semiconductor, Inc.
X
REF
OFF
X
OFF
REF
For More Information On This Product,
V X
=
= Calculated value of measured voltage (volts)
= Count for unknown voltage (counts)
= Count for lowest reference voltage (counts)
= Count for highest reference voltage (counts)
Go to: www.freescale.com
= Value of known reference voltage (volts)
= Value of lowest voltage (volts)
V REF
+
V OFF
Figure
--------------------------------------- -
N REF N OFF
29.
N X N OFF
–
–
OFF
, as follows:
General A/D Techniques
Application Note
REF
, and a
69