Allen-Bradley MicroLogix 1400 Instruction Manual page 421

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• For Read Messages: When a read message is used, the destination
file is the data file in the local or originating processor.
TIP
• For Write Messages: When a write message is used, the destination
file is the data file in the target processor.
The maximum number of elements that can be transmitted or received are
shown in the following table. You cannot cross file types when sending
messages. For example, you cannot read a timer into an integer file and
you cannot write counters to a timer file. The only exceptions to this rule
are that:
• long integer data can be read from or written to bit or integer files,
and
• RTC files can be written to integer files.
TIP
Message Type
485CIF
500CPU
PLC5
Input, output, string, and RTC file types are not valid for read
messages.
The table below is not intended to illustrate file compatibility, only the
maximum number of elements that can be exchanged in each case.
File Type Element Size Maximum Number
O, I, B, N 1-word
L 2-word
T, C, R 3-word
(1) 42-word
ST
O, I, B, N 1-word
F, L 2-word
T, C, R 3-word
RTC 8-word
ST 42-word
O, I, B, N 1-word
(1) 2-word
F , L
T 5-word
ST 42-word
Communications Instructions
of Elements per Message
103
51
34
2 (write only)
103
51
34
1 (write only)
2
103
51
20
1
Publication 1766-RM001A-EN-P - October 2008
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