Publication 1747-RM001G-EN-P - November 2008
12-14 SLC Communication Instructions
• Channel
(1)
Specifies the communication channel that is used to transmit the
message request.
– SLC 5/03 - (Channel 0, RS-232) or (Channel 1, DH-485)
– SLC 5/04 - (Channel 0, RS-232) or (Channel 1, DH+)
– SLC 5/05 - (Channel 0, RS-232) or (Channel 1, Ethernet)
Parameters for Target Device (except Modbus RTU)
• Message Timeout
(2)
Specifies the length of the message timer in seconds. A timeout of 0
seconds means that there is no timer and a message that has been
acknowledged waits indefinitely for a reply. Valid range is 0, 1 to 255.
Message Timeout for a channel 0 DF1 Full-duplex MSG instruction
should be configured greater than the channel 0 [ACK Timeout x (ENQ
Retries + 1)] in seconds.
Message Timeout for a channel 0 DF1 Half-duplex Master MSG
instruction with polling mode set to ‘message based’ should be
configured greater than the channel 0 [ACK Timeout x (2 x Message
Retires + 1)] in seconds.
Message Timeout for a channel 0 DF1 Half-duplex Master MSG with
polling mode set to standard should be configured greater than the
channel 0 [ACK Timeout x (Message Retires + 1) x number of slave
stations] in seconds.
Message Timeout for a channel 0 DF1 Half-duplex Slave MSG should
be configured greater than the Master’s channel 0 [2 x ACK Timeout x
(message retries + 1) x number of slave stations] in seconds.
Table 12.6 MSG Instruction Maximum Number of Elements for Modbus RTU Master
File Types Channel 0 on SLC 5/03, SLC 5/04, SLC 5/05
B 1856 bits
N 116 words
F 58 registers (32-bit)
(1)
SLC 5/03 and higher only.
(2)
SLC 5/03 and higher only.
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