PA 1500
Functions of the board
9.3
Digital inputs
The board
PA 1500
supplies 16 optically isolated inputs.
The inputs comply with the 24 V industry standard (IEC1131-2):
-
logic "1" corresponds to an input voltage > 16 V
-
logic "0" corresponds to an input voltage < 15 V.
All the inputs have a common current ground:
0V Ext. (inputs), pin 10 of the 37-pin SUB-D male connector.
The current input is at 6 mA with a nominal voltage of 24 V.
WARNING!
Do you operate all inputs with the same voltage supply?
The voltage
supply must deliver at least 16 x 6 = 96 mA
.
The maximum input voltage is 30 V.
Transil diodes, Z diodes, LC filters and optical couplers protect the system
bus from noise emitted by the peripheral. The effects of inductive and
capacitive noise are thus reduced.
The board requires no initialisation to read the 24 V digital information.
After successful power ON reset, data is immediately available on the
board.
Fig. 9-2: Protection circuitry for the inputs
9.3.1
Read the inputs 1 to 16
Two
addresses are available in the I/O address range (only in 8-bit data bus
access):
-
Base +0
for the inputs 1 to 8
-
Base +1
for the inputs 9 to 16.
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