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Chapter 9. Configuring the I/O Driver with the Power Tool 137

See Also

Adding and Modifying Datablocks

Reading and Writing Text Strings

The SI7 driver requires you to use the ASCII or STRING data type when accessing

text values. When reading an ASCII datablock, the following guidelines also apply:

• The text must be null terminated. It is your responsibility to ensure the text is

terminated properly.

• The whole string is copied into the Text database block associated with the

ASCII datablock. If the text is too big in the Text block, the string is truncated

and the last byte of the text is set to zero.

• Each byte in a datablock is assumed to be one ASCII character.

• You can write ASCII data over multiple Text blocks. For example, if you

define the length of an ASCII datablock to be 100 bytes, you can store the data

in two 50-character Text blocks.

• The driver pads zeroes at the end of ASCII data.

ASCII Data Type Examples

The length of the datablock is 10 bytes and the length of the associated Text block is 6 bytes.

The following text shows the values read and written by the SI7 driver.

Value Read by Driver... Text Read by iFIX...

Fred\0 Fred\00 (terminated with a null character and padded

with a zero)

Alarms Alarms

ABCDEFGHI\0 ABCDE\0

NOTE: Database Manager does not prompt you to add nonexistent datablocks referenced by

Text blocks.

1 2 ... 142 143 144 145 146 147 148 149 150 151 152 ... 267 268

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