On-Demand Function - Mitsubishi Electric FX3U-232-BD User Manual

FX Series PLC User's Manual - Data Communication Edition
Computer Link
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.
PLC
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
FX and FX
3U
Device
On-demand send
*1
M8127
processing
M8128 On-demand error flag
On-demand byte/word
M8129
changeover
On-demand head device
D8127
number specification
On-demand data quantity
D8128
specification
*1. FX , FX
0N
D-78
D8127
D8128
Sequence
D(n)
program
D(n+m-1)
, FX , FX
3G 3GC
PLCs
3UC
Name
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.
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.
Specifies the unit (byte or word) of data handled in the on-demand function.
ON: Unit = Byte (8-bit)
OFF: Unit = Word (16-bit)
Sets the head data register device number containing the data to be sent
using the on-demand function in a sequence program.
Sets the amount of data to be sent using the on-demand function in a
sequence program.
, FX and FX PLCs do not support this device.
1S 1N 1NC
Head device number (n)
Data length (m)
and FX PLCs and when ch1 is used in FX
3U 3UC
7.13 On-demand Function
Computer
Description
7 Commands
, FX ,
3G 3GC