Siemens SIMATIC S5 CP 523 Manual page 166

CP 523
* 5.2
EWA 4NEB 811 6044-02a
START
CPU transfers message frame length or end-
of-text character to the transfer memory on
the CP (words 2 and 4)
CPU transfers the "Send message frame"
request to the transfer memory of the CP
(word 0*)
CPU reads the transfer memory and evaluates
the coordination bytes (bytes 0 and 1)
Has the
CP accepted
the Send job?
(bit 0 in byte
CPU transfers message block to the transfer
memory of the CP
CP transfers data from the transfer memory
to the Send mailbox
Transfer another
Yes
message block to the
transfer memory?
CP transfers data from the Send mailbox to
the peripheral device
Figure 7-8. Schematic for "Send Message Frame"
No
1=1)
Yes
No
END
Communications Mode
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