Table of Contents
Advertisement
11 INSTRUCTIONS AND FUNCTIONS
Processing Code 48
Program Example
100 ' This program sets the high impedance control
110 DIM TBL1%(10),TBL2%(10)
120 CH%=4
130 TBL1%(0)=4800
140 TBL1%(1)=&H107
150 TBL1%(2)=&H1
160 ZOPEN #CH%,TBL1%( )
170 TBL2%(0)=48
180 TBL2%(1)=1
190 ZCNTL #CH%,0,TBL2%( )
200 ZCLOSE #CH%
210 END
11 - 422
Specifying high impedance control
Control table format definition
Element position
Item
%(0)
Processing code
%(1)
Setting
• This processing code is used to set whether or not the high impedance control is
used when the RS-422/485(CH3) and other stations are connected in a 1 : n
configuration.
• Specify 48 for the processing code.
• Specify whether or not the high impedance control is used in the setting.
0 • • • High impedance control disabled
1 • • • High impedance control enabled
• The default value of the setting is 0 (high impedance control disabled).
• For a transmission station to send data when the communication module and
other stations are connected in a 1 : n configuration and the high impedance
control is enabled for the communication channel, the transmission station
should cancel the high impedance before sending the data. The impedance
should then be set high again after sending the data. Stations other than the
station sending data should be in the high impedance status.
At this point, the communication module sends up to 2 bytes of data between
the canceling of the high impedance control and the start of transmission, as
well as between the end of data transmission and setting the impedance high
again. If another station wants to send data thereafter, it must not start its
transmission until after the station that was previously sending data finishes
transmission of these 2 bytes of data.
High impedance status
Maximum
2-byte data
Description
Specify the processing code.
Specify whether or not to set the high
impedance control.
Data
Maximum
2-byte data
:
' Defines arrays
:
' Selects channel 4
:
' Opens the communication channel
:
' Specifies to set the high impedance
control
:
' Enables the high impedance control
:
' Executes
:
' Closes the communication channel
MELSEC-Q
High impedance status
11 - 422
Advertisement
Table of Contents
