Master to Slave Exchanges

At a Glance

The Master station carries out exchanges to the Slave station:

Exchange to Address Ad0

An exchange from the Master to Ad0, as seen at point 1 in the diagram above, is used for communication from the Master application program to the Slave system (access to the different objects, etc.).

The functions READ_VAR, WRITE_VAR and SEND_REQ can be used to communicate to Ad0.

The function address is type ADDR('r.m.c.x'), where:

Parameters	Description
r	Rack number
m	Module number
c	Channel number
x	Ad0 Slave address

Example

ADDR('0.0.1.Ad0') for a slave connected to a PCMCIA card in the Master PLC

Exchange to Address Ad2

An exchange from the Master to Ad2, as seen at point 2 in the diagram above, is used for sending messages from the Master application program to the Slave application program.

In Unitelway master mode, the only type of operation authorized is type 2 (send).

The functions SEND_REQ and DATA_EXCH can be used to communicate to Ad2.

The function address is type ADDR('r.m.c.x'), where:

Parameter	Description
r	Rack number
m	Module number
c	Channel number
x	Ad2 Slave address

Example

SEND_REQ(ADDR('0.0.1.Ad2'), 16#FC, %MW..........)

Here: use of the request code, 16#FC, unsolicited data