Advantech PCI-1757UP Bedienungsanleitung PDF herunterladen (Seite 23)

17 Chapter 3

3.2.3 Input/Output Control

A control word can be written to a port's configuration register (Base+3)

to set the port as an input or an output port, unless the ports are set via the

switch. Table 3-1 shows the format of a control word.

Table 3.1: Bit Map of Port Configuration Register

Bit Description

D0 Port C lower bits 0: output; 1: input

D1 Port B 0: output; 1: input

D2 Ignore

D3 Port C higher bits 0: output; 1: input

D4 Port A 0: output; 1: input

D5 Ignore

D6 Ignore

D7 HW/SW 0: SW; 1: HW

Note: A control word has no effect if the correspond-

ing port is set as an output port by the SMD

switch SW2. D7 is a read only bit for identifying

the SMD switch SW2 position 1 is ON or OFF.

D7 = 0 means the I/O configuration is set by

configuration register (SW); D7 = 1 means the I/

O configuration is set by SMD switch SW2

(HW). When D7= 1, read the value of D4, D3,

D1 and D0 mapping the SW2 location 3,4,5 and

6, respectively.

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.

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