Chapter 5 Application Notes

These values are for an 8K controller. See the 484 User's Guide for limits of smaller controllers.
584
http://www.modicon.com/techpubs/app7.html (2 of 7) [1/11/2000 10:44:32 PM]

884
M84
http://www.modicon.com/techpubs/app7.html (3 of 7) [1/11/2000 10:44:32 PM]

984
http://www.modicon.com/techpubs/app7.html (4 of 7) [1/11/2000 10:44:32 PM]

5.2 Estimating Serial Transaction Timing
The following sequence of events occurs during a Modbus serial transaction. Letters in
parentheses ( ) refer to the timing notes at the end of the listing.
1 The Modbus master composes the message.
2 The master device modem RTS and CTS status are checked. (
A)
3 The query message is transmitted to the slave. (
B)
4 The slave processes the query message. (
C, 
D)
5 The slave calculates an error check field. (
E)
6 The slave device modem RTS and CTS status are checked. (
A)

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