Allen-Bradley MicroLogix 1400 Instruction Manual page 524

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522 Recipe and Data Logging
Publication 1766-RM001A-EN-P - October 2008
Example Maximum record of String data
String Length of Record
The size of a record is limited so that the length of the maximum
formatted string does not exceed 109 characters. The following table can
be used to determine the formatted string length.
Data Memory Consumed
delimiter 0 bytes
date 2 bytes
time 2 bytes
string element 84 bytes
For queue 0, the formatted string length is 29 characters, as shown below:
Data Date Time
Characters 10 1 8
= 10 + 1 + 8 + 1 + 89 = 109 characters
Number of Records
Using Queue 0 as an example, each record consumes:
Record Field Memory Consumption
Date 2 bytes
Time 2 bytes
ST10:0 84 bytes
Integrity Check 2 bytes
Total 90 bytes
Each record consumes 90 bytes. So if only one queue was configured, the
maximum number of records that could be stored would be 1456. The
maximum number of records is calculated by:
Maximum Number of Records = Data Log File Size/Record Size
Formatted String Size
1 character
10 characters
8 characters
89 characters
String
1 89
= 128K bytes/90 bytes
= (128)(1024)/90
= 1456 records