Intel 8XC196MC Benutzerhandbuch
12-7
ANALOG-TO-DIGITAL (A/D) CONVERTER
12.4.4 Programming the A/D Command Register
The A/D command register controls the operating mode, the analog input channel, and the con-
version trigger.
version trigger.
AD_TIME
Address:
Reset State:
1FAFH
FFH
The A/D time (AD_TIME) register programs the sample window time and the conversion time for each
bit. This register programs the speed at which the A/D can run — not the speed at which it can convert
correctly. Consult the data sheet for recommended values. Initialize the AD_TIME register before
initializing the AD_COMMAND register. Do not write to this register while a conversion is in progress;
the results are unpredictable.
bit. This register programs the speed at which the A/D can run — not the speed at which it can convert
correctly. Consult the data sheet for recommended values. Initialize the AD_TIME register before
initializing the AD_COMMAND register. Do not write to this register while a conversion is in progress;
the results are unpredictable.
7
0
SAM2
SAM1
SAM0
CONV4
CONV3
CONV2
CONV1
CONV0
Bit
Number
Bit
Mnemonic
Function
7:5
SAM2:0
A/D Sample Time
These bits specify the sample time. Use the following formula to
compute the sample time.
compute the sample time.
where:
SAM =
1 to 7
T
SAM
=
the sample time, in
µ
sec, from the data sheet
F
XTAL
1
=
the input frequency on XTAL1, in MHz
4:0
CONV4:0
A/D Convert Time
These bits specify the conversion time for each bit. Use the following
formula to compute the conversion time.
formula to compute the conversion time.
where:
CONV =
2 to 31
T
CONV
=
the conversion time, in
µ
sec, from the data sheet
F
XTAL
1
=
the input frequency on XTAL1, in MHz
B
=
the number of bits to be converted (8 or 10)
Figure 12-4. A/D Time (AD_TIME) Register
SAM
T
SA M
F
X TA L1
×
2
–
8
-------------------------------------------------
=
CO NV
T
CO NV
F
X TAL1
×
3
–
2
B
×
----------------------------------------------------
1
–
=