 |
Select A/D
Channel
Number
|
|
Set C3 to C0 of port address+0 (low 8 bits) to
select A/D channel number.
|
|
C3
|
C2
|
C1
|
C0
|
Input
cannel |
0
|
0
|
0
|
0
|
CH0 |
0
|
0
|
0
|
1
|
CH1 |
0
|
0
|
1
|
0
|
CH2 |
0
|
0
|
1
|
1
|
CH3 |
0
|
1
|
0
|
0
|
CH4 |
0
|
1
|
0
|
1
|
CH5 |
0
|
1
|
1
|
0
|
CH6 |
0
|
1
|
1
|
1
|
CH7 |
1
|
0
|
0
|
0
|
CH8 |
1
|
0
|
0
|
1
|
CH9 |
1
|
0
|
1
|
0
|
CH10 |
1
|
0
|
1
|
1
|
CH11 |
1
|
1
|
0
|
0
|
CH12 |
1
|
1
|
0
|
1
|
CH13 |
1
|
1
|
1
|
0
|
CH14 |
1
|
1
|
1
|
1
|
CH15 |
|
|
| Hold the Input Signal |
|
Set x bit of port address+0 (low 8 bits) to 0
to latch input signal. |
|
|
 |
| Start A/D
Conversion |
|
Set SE0 and
SE1 of port address+0 (high 8 bits) to select trig method for A/D
converter.
|
x
|
x
|
x
|
TRI
|
INT
|
ENX
|
SE1
|
SE0
|
|
| SE1 |
SE0 |
Selection |
0
|
0
|
Software
trigger by TRI bit |
0
|
1
|
Software
trigger by TRI bit |
1
|
0
|
External
trig from J1-2 |
1
|
1
|
Trig
by 8254 |
|
1. By using software
trigger
|
1.1 Set or reset INT bit to enable/disable
interrupt.
|
| INT |
Enable/Disable |
0
|
Disable
interrupt |
1
|
Enable
interrupt |
|
1.2 Write 0 to TRI bit to start
conversion.
|
2. By using 8254 trigger
|
2.1 Set or reset INT bit to
enable/disable interrupt.
2.2 Set the ENX bit to 1.
2.3 Start 8254 counter.
|
The clock rate of 8254 is
1M, it is connected to counter 0, then the output of counter 0 is
connected to counter 1, so that user need divide the clock by counter 0
then divide it by counter 1. The divided clock rate of counter 1 is
used to trig A/D conversion
|
3. By using external
trigger
|
3.1 Set or reset INT bit to enable/disable
interrupt.
3.2 Set the ENX bit to 1.
3.3 Send "1" to "0" pulse from J1-02 pin.
|
|
Get Results
|
There are two methods to get
the
results
of A/D conversion.
|
1. By using polling
|
After start conversion, wait about
50us
to get
the conversion result.
|
2. By using interrupt
|
|
2.1
Write an
interrupt service routine.
2.2
After
conversion, the adapter will generate an
interrupt to start the interrupt service routine.
2.3
The
interrupt service routine read 12 bits result
from port address + 0.
|
0
|
0
|
0
|
0
|
11
|
10
|
9
|
8
|
7
|
6
|
5
|
4
|
3
|
2
|
1
|
0
|
|
|
2.4 The interrupt service
routine read port address + 2 to clear interrupt signal.
|
|
How to Use D/A
Converter
|
1. Write 12 bits D/A to
port
address +
2 (D/A channel 1).
|
0
|
0
|
0
|
0
|
11
|
10
|
9
|
8
|
7
|
6
|
5
|
4
|
3
|
2
|
1
|
0
|
|
2. Write 12 bits D/A to
port
address +
4 (D/A channel 2).
|
0
|
0
|
0
|
0
|
11
|
10
|
9
|
8
|
7
|
6
|
5
|
4
|
3
|
2
|
1
|
0
|
|
3.After 30us, the D/A
converter
will
finish output procedure.
|
|
How to Use Digital
Output Channel
|
Write data to port address + 6.
|
15
|
14
|
13
|
12
|
11
|
10
|
9
|
8
|
7
|
6
|
5
|
4
|
3
|
2
|
1
|
0
|
|
|
How to Use Digital
Input Channel
|
|
1. Write FF to port
address + 6.
2. Read digital input from port address + 6.
|
|
|
|