User`s manual

FX communication
Commands 8
8-18
8.10.3 Specification and Example of On-demand
1 ) Command specification
Protocol format 1 is shown.
Programmable
controller
Special auxiliary
relay M8127
Write processing
ON
Computer
Programmable
controller
S T X
Station No. PLC No.
Sum check code
Transmission
data
Added by
programmable
controller
E T X
OFF
On-demand data is set, the head address is
written to D8127 and the data length is
written to D8128.
Notes
• Specify the data length so as to satisfy the following condition.
Data length
≤
40H (64 points)(13 points for FX
0N
)
• The PLC number, “FE” is added by the programmable controller.
• The station number, PLC number, number of devices, and sum check code are
expressed in hexadecimal.
Important
• Don't use the on-demand function unless the system configuration is 1:1.
• If the on-demand function is used in a multidrop system in which the computer and the
programmable controller are connected in 1:n configuration, normal communication
data in control protocol formats 1 to 4, and on-demand data become confused, and
normal data transmission is not possible.