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CP 523 Technical Description

Data transfer between the CP and peripheral device takes place as follows:

The CP 523 sets the "DTR" output after startup. This indicates that the CP is operable and ready to

receive.

Example: The CP wants to send data

1. CP waits till DSR = ON

If the peripheral device still has not set DSR to ON after 20 s, the CP reports the error to the

CPU (peripheral device not ready).

2. CP sets RTS

3. CP waits till CTS = ON

If the peripheral device still has not set CTS to ON after 20 ms, the CP reports the error to the

CPU (peripheral device not ready).

4. CP sends data

5. CP resets RTS after sending data

6. Peripheral device sets CTS to OFF

Figure 2-5. Timing Diagram for Data Transfer between the CP and the Peripheral Device

XXXXXXXX

XXXXXXXX XXXXXXXXRXD

TXD

DTR

RTS

DSR

CTS

CP switched

max:

20 s

Peripheral device switched on

max:

20 s

CP reports data

cannot be received

OFF

XXXXXXXX

Example: Peripheral device wants to send data

The peripheral device only checks the DTR line

If ON: Data may be sent (CP ready to receive)

If OFF: Data transmission must be interrupted (CP not ready to receive)

EWA 4NEB 811 6044-02a

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Siemens KS7 Series Specifiche Pagina 23