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Communications with the Host Section 1-4
1-3-2 Connecting to the Host
The NT631/NT631C has the following two communications ports.
The serial port B is equipped with an RS-232C connector and an RS-422A/
485 terminal block (selectable by memory switch).
Serial Port A:
D-SUB 9-pin connector
For RS-232C use only (The Support Tool and bar code readers can be con-
nected here.)
Serial Port B:
D-SUB 9-pin connector for RS-232C use only (The Support Tool and bar code
readers can be connected here) or Terminal block for RS-422A/485 use only.
The host can be connected at either of these two ports.
The connection methods for each communications method at the PT and host
sides are indicated below. Make the settings in accordance with the communi-
cations method that can be used with the PLC to be connected and the condi-
tions at the operation site.
Reference: When using an RS-232C/422A adapter (NT-AL001) with the host link or NT
link (1:1) communications method, RS-485 cannot be used. The connection
must be made with RS-232C or RS-422A.
1-4 Communications with the Host
The NT631/NT631C is connected to the host by one of the following commu-
nications methods.
The following communications can be used to connect an OMRON PLC:
• Host Link
• 1:1 NT Link
• 1:N NT Link (standard or high-speed)
The following communications can be used to connect another companies’
PLC or FA computer:
• Communications protocol supported by the other company’s PLC
• Memory link
In all of these communications methods that can be used with NT631/
NT631C, data communications with host are by direct connection (Memory
link is, however, a quasi-direct connection).
In the following, the host link and NT link that carry out the direct connection
will be discussed. Memory link will be explained in 1-5 Communications Using
Memory Links.
1-4-1 Direct Connection Function
With the NT631/NT631C, the bits and words referring to data required for dis-
play, and those for storing input data, can be allocated to any part of the PLC
memory area.
The NT631/NT631C can directly write to and read from such allocated bits
and words to change the display status of the elements on the PT screen,
control the PT operating status, and notify the host of the status.
This function, which directly reads and writes the statuses of words and bits
without using a PLC program is called the direct connection function.