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AD_TIME
The A/D time (AD_TIME) register programs the sample window time and the conversion time for each
bit.
7
SAM2
SAM1
Bit
Bit
Number
Mnemonic
7:5
SAM2:0
4:0
CONV4:0
NOTES:
1.
The register programs the speed at which the A/D can run — not the speed at which it can con-
vert correctly. Consult the data sheet for recommended values.
2.
Initialize the AD_TIME register before initializing the AD_COMMAND register.
3.
Do not write to this register while a conversion is in progress; the results are unpredictable.
SAM0
CONV4
A/D Sample Time
These bits specify the sample time. Use the following formula to
compute the sample time.
×
T
F
–
SAM
O SC
------------------------------------------- -
SAM
=
8
where:
SAM =
1 to 7
the sample time, in µsec, from the data sheet
T
=
SAM
F
=
the XTAL1 frequency, in MHz
OSC
A/D Convert Time
These bits specify the conversion time. Use the following formula to
compute the conversion time.
×
T
F
CO NV
OSC
-----------------------------------------------
CO NV
=
×
2 B
where:
CONV =
2 to 31
the conversion time, in µsec, from the data sheet
T
=
CONV
F
=
the XTAL1 frequency, in MHz
OSC
B
=
the number of bits to be converted (8 or 10)
Reset State:
CONV3
CONV2
Function
2
–
3
–
1
REGISTERS
AD_TIME
Address:
1FAFH
FFH
0
CONV1
CONV0
C-9
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