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Result

IOdata: The bits of the 'IOdata' variable of the selected chip are set low (0) but the bits that

correspond to inputs remain unchanged.

Description

The status of the Input/Output ports are held in the 'IOdata' variable. Each bit of this variable

corresponds to the status of an IO-channel. If the outputs of the IO-chip are to be cleared then it

is not recommended to immediately set the 'IOdata' variable to 0, because the status of the

input channels would no longer correspond to the physical status. In order to avoid such conflict

this procedure must be used.

Note that the 'IOdata' variable is just a buffer memory. When this changes its value the outputs

do not immediately change status. This occurs only when this value is sent to the IO-chip.

Example

BEGIN

ConfigIOchipAsOutput(0);

ConfigIOchannelAsInput(1); {channel 1 configured as input}

ConfigIOchannelAsInput(2); {channel 2 configured as input}

ConfigIOchannelAsInput(3); {channel 3 configured as input}

ConfigIOchannelAsInput(4); {channel 4 configured as input}

ClearIOdataArray(0); // Clear channels 1 to 8 from IOdata array

// The status of the inputs stays unchanged

END;

SetIOchArray IO

Syntax

PROCEDURE SetIOchArray(Channel_no: Longint);

Parameter

Channel_no: Value between 1 and 64 which corresponds to the Input/Output channel that is to

be set.

Result

IOdata: If the selected channel is an output then the correct bit in the 'IOdata' variable of the

corresponding chip is set high (1).

Description

The status of the Input/Output ports is held in the 'IOdata' variable. Each bit of this variable

corresponds to the status of an IO-channel. If a particular output of the IO-chip is to be set then

it is not advisable to immediately set the corresponding bit in the 'IOdata' variable to high. If the

selected channel has been configured as an input then the status would no longer correspond to

the physical status. In order to prevent such conflict this procedure must be used.

Note that the 'IOdata' variable is just a buffer memory. When it changes its value the outputs do

not immediately change status. This only occurs when this value is sent to the IO-chip.