Technical information

OPTO DIO Reference Read This First.

Source Driver Output Logical Levels._________________________________

The source cards are supplied with non inverting buffer

chips, 74LS541, so that a logical one written to the output

output port drives the output low. Thus in this normal mode of

operation the voltage level of the output line follows the logic

level in the output register.

The source cards can be fitted with inverting buffer chips,

74LS540, so that a logical one written to the output register

drives the output low and a logical zero written to the output

port drives the output high. See Figure 1-7. Thus in this inverse

mode of operation the voltage level of the output line does the

opposite of the logic level in the output register.

Note since the sink driver chips are inverting and the

source are not the non inverting buffer chips are must be

changed when source and sink drivers are changed.

Figure 1-7. Logically Inverting The Source Output.____________________________________________

DRIVER BUFFER USED PORT DATA PORT LINES OPERATION

SOURCE 74LS541 0 = low OFF = low NORMAL

SOURCE 74LS541 1 =high ON =high NORMAL

SOURCE 74LS540 INVERTERS 0 = low ON =high INVERSE

SOURCE 74LS540 INVERTERS 1 =high OFF = low INVERSE

Note: By default Source driver use 74LS541 non inverting buffers,

74LS540 INVERTING buffers will invert the output signals.

Sink Driver Output Connection.____________________________

ULN2804 Drivers.

The ULN2804 chips are high voltage, high current NPN

DARLINGTON open collector drivers, output voltage range to

50 Volts. Use ULN2824 chips for output up to 95 Volts. When

changing from 2984 to 2804 drivers note than the 2804 are

INVERTING drivers, thus to produce the same logical output

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