Advantech PCI-1751U Manual de usuario descargar pdf (Pagina 21)

17 Chapter 3

3.2.3 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.

3.2.4 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.

3.2.5 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

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 37 38

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