Advantech PCI-1751U, User Manual

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17 Chapter 3
3.2.2 Interrupt Function of the DIO Signals
Two I/O pins (PC00 and PC10) can be used to generate hardware inter-
rupts. A user can program the interrupt control register (Base + 32) to
select the interrupt sources. Refer to "Interrupt Function" in this chapter
for details about interrupt control.
3.2.3 Input/Output Control
A control word can be written to a port's configuration register (Base+3
for port 0 and Base+7 for port 1) to set the port as an input or an output
port, unless the ports are set as output ports via jumpers (refer to Section
2.3, Jumper Settings). Table 3-1 shows the format of a control word.
Note: A control word has no effect if the corresponding port is set as an
output port by a jumper.
Warning!
Before setting any port as an output port via software, make
sure that a safe output value has also been set. An output
voltage will appear at the pins immediately following the
control word taking effect. If no output value was specified,
the value will be indeterminate (either 0 or 1), which may
cause a dangerous condition.
3.2.4 Initial Configuration
The initial configuration of each port depends on the input/output jumper
setting of each port, on the setting of the jumper JA1, and on whether the
power was actually disconnected or whether the system was hot reset.
If jumper JA1 is not enabled, all ports configured by software are auto-
matically set as input ports during system start up or reset, with a default
signal level of logic 1 (high). All ports set via jumpers as output ports are
set as output ports during system start up or reset, signal level logic 0 (0
V).
Table 3.1: Bit map of port configuration register
D7 D6 D5 D4 D3 D2 D1 D0
Don't
care
Don't
care
Don't
care
PortA
0: output
1: input
1: input Don't
care
Port B
0: output
1: input
Port C
lower bits
0: output
1: input