Omron CQM1H-SCB41 Overview of NT Links, NT Links 1N Mode, NT Links 11 Mode, Precautions

Connections Section 8-1

8-1 Overview of NT Links

This section explains the application of a Serial Communications Board for an NT Link in either 1:N or 1:1 mode. For details on the operation of the PT, refer to the operation manual for the PT.

Note In an NT Link using 1:N mode, a PC can be connected to either one or more than one PTs. There is no difference in functionality determined by the number of PTs connected. The 1:1 mode, however, uses a different communications protocol from the 1:N mode and these two modes are not compatible.

8-1-1 NT Links — 1:N Mode

A PC can be connected to one or more Programmable Terminals (PTs) using an RS-232C or RS-422A/485 port. The I/O memory of the PC is allocated as a Sta- tus Control Area and a Status Notification Area for the PT, as well as to objects, such as touch switches, lamps, and memory tables. This enables the status of the I/O memory in the PC to be controlled and monitored by operations from the PT, without the use of ladder programming in the PC. One PC can be connected to up to eight PTs.

The user does not need to be aware of the 1:N NT Links commands. All that is necessary is to allocate PC memory for the PTs.

Serial Communications Board	Serial Communications Board
1:1 connection	1:N connections

PT

PTPT

8-1-2 NT Links — 1:1 Mode

Although the functionality of an NT Link in 1:1 mode is the same as an NT Links in 1:N mode, only one PT can be connected to the PC. The 1:1 mode is not compat- ible with the 1:N mode as a communications protocol.

Serial Communications Board

1:1 connection

PT

8-1-3 Precautions

1, 2, 3... 1. Set the serial port on the PT to a 1:N NT Link whenever the Serial Commu- nications Board is set to a 1:N NT Link, and set the serial port on the PT to a 1:1 NT Link whenever the Serial Communications Board is set to a 1:1 NT Link. The Serial Communications Board will not be able to communicate if the PT port is set to a different mode.

2.The NT20S, NT600S, NT30/30C, and NT620S/620C/625C cannot be used if the cycle time of the PC is 800 ms or longer. This is true in both 1:1 and 1:N mode (even when a 1:1 connection is used in 1:N mode).

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