83C196EA Intel Corporation, 83C196EA Datasheet - Page 34

• Manufacturer Part Number: 83C196EA
• Description: CHMOS 16-BIT MICROCONTROLLER
• Manufacturer: Intel Corporation

83C196EA CHMOS 16-BIT MICROCONTROLLER — AUTOMOTIVE
30
6.7 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 12 and 14 to determine appropriate values for SAM and CONV; otherwise, erroneous
conversion results may occur.
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.
Use the following formulas to determine the SAM and CONV values.
where:
At 40 Mhz, to meet T
10-bit mode:
8-bit mode:
SA M
SAM
CONV
T
T
f
B
SAM
CONV
=
T
------------------------------ -
S A M
equals a number, 1 to 7
equals a number, 2 to 31
is the sample time, in sec
(Tables 12 and 14)
is the conversion time, in sec
(Tables 12 and 14)
is the operating frequency, in MHz
is the number of bits to be converted
(8 or 10)
8
SAM
CONV
SAM
CONV
f 2
–
SAM
=
=
=
=
and T
5 6 7
5 6 7
18 19 20
23 24
CONV
CONV
minimum specifications:
=
T
T
SAM
SAM
31
T
--------------------------------- -
C ON V
31
2
1 s
1 s
T
B
CONV
f 3
–
T
CONV
–
1
10 s
10 s
ADVANCE INFORMATION
SAM
and T
CONV
specifica-