D-78
FX Series PLC User's Manual - Data Communication Edition
Computer Link
7 Commands
7.13 On-demand Function
7.13
On-demand Function
When there is data to be sent from a PLC to the computer, the on-demand function can specify the data
register area storing the data to be sent, and let the PLC start sending.
When data is sent between the computer and a PLC, only the computer can start data transmission.
When there is emergency data to be sent from a PLC to the computer, the on-demand function is applicable
to let the PLC begin sending data to the computer.
Point
This function is applicable when the computer and the PLC CPU have the 1-to-1 configuration.
7.13.1 Special data registers and special auxiliary relays used in on-demand function
The tables below show the special data registers and special auxiliary relays used in the on-demand function.
1. In all PLCs except FX
3G
, FX
3GC
, FX
3U
and FX
3UC
PLCs and when ch1 is used in FX
3G
, FX
3GC
,
FX
3U
and FX
3UC
PLCs
*1.
FX
0N
, FX
1S
, FX
1N
and FX
1NC
PLCs do not support this device.
Device
Name
Description
M8127
*1
On-demand send
processing
Remains ON while the on-demand function is being executed.
ON: On-demand data is being sent.
OFF: Sending of on-demand data is completed.
M8128
On-demand error flag
Turns ON when an error is included in a specified value to be sent in the on-
demand function.
ON: Error is included.
OFF: Error is not included.
M8129
On-demand byte/word
changeover
Specifies the unit (byte or word) of data handled in the on-demand function.
ON: Unit = Byte (8-bit)
OFF: Unit = Word (16-bit)
D8127
On-demand head device
number specification
Sets the head data register device number containing the data to be sent
using the on-demand function in a sequence program.
D8128
On-demand data quantity
specification
Sets the amount of data to be sent using the on-demand function in a
sequence program.
Sequence
program
PLC
Computer
D8127
D8128
D(n)
D(n+m-1)
Head device number (n)
Data length (m)
Summary of Contents for FX-485ADP
Page 2: ......
Page 120: ...B 2 FX Series PLC User s Manual Data Communication Edition N N Network ...
Page 188: ...C 2 FX Series PLC User s Manual Data Communication Edition Parallel Link ...
Page 244: ...D 2 FX Series PLC User s Manual Data Communication Edition Computer Link ...
Page 344: ...E 2 FX Series PLC User s Manual Data Communication Edition Inverter Communication ...
Page 700: ...H 2 FX Series PLC User s Manual Data Communication Edition Programming Communication ...
Page 752: ...I 2 FX Series PLC User s Manual Data Communication Edition Remote Maintenance ...
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