CP 523
Communications Mode
Figure 7-8. Schematic for "Send Message Frame"
START
* 5.2
No
Yes
Yes
No
CPU reads the transfer memory and evaluates
the coordination bytes (bytes 0 and 1)
CPU transfers message frame length or end-
of-text character to the transfer memory on
the CP (words 2 and 4)
CPU transfers message block to the transfer
memory of the CP
CP transfers data from the transfer memory
to the Send mailbox
CP transfers data from the Send mailbox to
the peripheral device
Transfer another
message block to the
transfer memory?
CPU transfers the "Send message frame"
request to the transfer memory of the CP
(word 0*)
Has the
CP accepted
the Send job?
(bit 0 in byte
1=1)
END
EWA 4NEB 811 6044-02a
7-61