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C1120 S5 to II/O Lightbus Interface Beckhoff II/O-Lightbus System

Date 27.06.97 Version 2.1 Page 17 of 52

Arbitration of a single load /transfer of peripherial bytes

As used with the indirect communications list every module in the II/O Lightbus System can

be accessed immediately via a single communication list: The IDENT- number of a dedicated

module has to be placed in the first address block address location, following four bytes keep

the I/O data.

For handshake purposes two bits in the Status Byte of the PLC can be used: PB/PY254 and

PB/PY 255 Bit 0:

First, IDENT number and I/O data are written to the single communication list. Then, bit 0 of

PB/PY 254 is set (strobe bit) by the PLC. After this, a transfer to PB PY 255 with any data

forces an interrupt and II/O Lightbus communication with the C1120 interface.

The C1120 interface card responds with setting the bit 0 of PB/PY 254 (ACK bit): the data

byte contents are valid and can be read by the PLC with L PB. The PLC handshakes with

resetting the bit 0 of PB/PY 254 (strobe bit). The C1120 ends the handshake cycle by resetting

the ACK bit 0 of PB/PY 254.

By setting "address single communication" to 0 in the setup screen, this option is not

supported during the use with this setup.

Example :

The value of the single communication address is set to 128.

S5 C1120

1.) Transfer identnumber for dedicated

II/O-Lightbus module address to

PB/PY 128

2.) Transfer transmit data from memory

flags or equiv. to PB/PY 129,130, 131,

132

3.) Set strobebit

LKB 1

T PB/PY 254

4.) Force interrupt on C1120: transfer

something to PB/PY255

L KH AFFE

T PY 255

5.) Polling of ack- bit in statusregister II/O-Lightbus communication doing

transfer to and from the module

6.) Set of Ack.- bit in statusregister

7.) Load of valid data from the single

communication list to destination

LPW

TDW

TMW

8.) Reset strobebit

Polling of ack- bit in statusregister

9.) Reset of Ack.- bit in statusregister

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 ... 51 52

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