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ASM 421 Technical Description
6GT2 097-3AH00-0DA2
– 47 –
RD: 03/02
6GT2 002-0DA00
ASM 421 / V.24
Subject to change without notice!
6GT2 002-0DB00
ASM 421 / RS422
6GT2 002-0DC00
ASM 421 / TTY
J31069-D0142-U001-A0-7618
4
Cold start and restart
Cold start and restart must be performed by the user and the ASM 421 in a coordinated manner. Only then
can ASM and user operations be synchronized properly.
Cold start and restart on the ASM 421 side:
After switching on the power supply, the ASM 421 performs a comprehensive self-test. This takes about 2
seconds. During this time the ASM cannot communicate with the user. The ASM will not respond to any
telegram from the user (also no NAK at the procedure level).
After the self-test, the ASM sends a start-up message (see section 3.5.1) and is immediately ready to
receive.
If the start-up message is not acknowledged by the user (e.g. user is not ready or switched off) the mes-
sage will be lost. As a result the red LED flashes 28 times.
The ASM now always expects to receive a RESET telegram containing the relevant parameters from the
user (see section 3.4.15). Any other telegram will not be processed and will be rejected with an error.
Following the RESET, the ASM is able to process all the commands described in section 3.4.
Cold start and restart on the user (computer) side:
The following structogram shows a secure synchronization procedure for restarting the user program:
Computer or PC switched on
Send RESET telegram to ASM 421
Yes
No
Telegram acknowledged correctly ?
ASM is synchronized
Wait max. 3 seconds for start-up telegram from the ASM
Start-up telegram re-
ceived ?
Yes
No
Send RESET telegram
to ASM and fetch ack-
nowledgement
ASM is not syn-
chronized
–
ASM was not switched off
–
ASM has performed its self-test more quickly than
the computer; the start-up telegram from the ASM is
lost
ASM is synchro-
nized
–
ASM is switched off
or defective
–
Message sent to
user
–
Start synchroniza-
tion procedure with
ASM cyclically