80C196MD INTEL [Intel Corporation], 80C196MD Datasheet - Page 34

• Manufacturer Part Number: 80C196MD
• Description: 8XC196MH INDUSTRIAL MOTOR CONTROL CHMOS MICROCONTROLLER
• Manufacturer: INTEL [Intel Corporation]

8XC196MH INDUSTRIAL MOTOR CONTROL CHMOS MICROCONTROLLER
A/D SAMPLE AND CONVERSION TIMES
Two parameters, sample time and conversion time,
control the time required for an A/D conversion. The
sample time is the length of time that the analog input
voltage is actually connected to the sample capacitor.
If this time is too short, the sample capacitor will not
charge completely. If the sample time is too long, the
input voltage may change and cause conversion
errors. The conversion time is the length of time
required to convert the analog input voltage stored on
the sample capacitor to a digital value. The
conversion time must be long enough for the
comparator and circuitry to settle and resolve the
voltage. Excessively long conversion times allow the
sample capacitor to discharge, degrading accuracy.
The AD_TIME register programs the A/D sample and
conversion times. Use the T
tions in Tables 16 and 18 to determine appropriate
values for SAM and CONV; otherwise, erroneous
conversion results may occur.
34
SAM
and T
CONV
specifica-
Use the following formulas to determine the SAM and
CONV values:
where:
When the SAM and CONV values are known, write
them to the AD_TIME register. Do not write to this
register while a conversion is in progress; the results
are unpredictable.
CONV
SAM
SAM = 1 to 7
CONV = 2 to 31
T
T
F
B is the number of bits to be converted (8 or 10)
SAM
CONV
OSC
(Tables 16 and 18)
(Tables 16 and 18)
is the sample time, in sec
is the XTAL1 frequency, in MHz
=
is the conversion time, in sec
=
T
----------------------------------------
SAM
T
-------------------------------------------
CONV
8
F
2
OSC
F
B
OSC
–
2
–
3
–
1
®