51
CARLO GAVAZZI
CONTROLS
SERIAL COMMUNICATION PROTOCOL
WM4-96
V1 R3
Page
Timing characteristics for 2-wire communication msec
T response: max answering time 600ms
T response: typical answering time 100ms
T delay1: minimum time for a new query on the same address 10ms
T delay2: minimum time for a new query on a different address 10ms
T null: maximum interruption time on the request frame 3 char
APPLICATION NOTES
1. If the instrument does not answer within the “max answering time”, it is necessary to repeat the
query. If the instrument does not answer after 2 or 3 consecutive queries, it must be considered
as not connected, faulty or having a different address. The same consideration is valid in case of
CRC errors or incomplete frames.
2. By entering the programming mode (by pressing the “S” key) the communication is interrupted.
Any data received during the programming mode are ignored.
3. EEPROM read and write commands must be carried out to manage “static” variables. Use them
only during the instrument set-up and not during the normal measuring mode in order to avoid to
extend the answer time and to limit the writing in EEPROM (max 100.000).
4. To avoid reflections or couplings between the communication wires it is suggested to terminate
the last instrument of the network and of the host. If some problems persist, bias the host
transmission. It is advisable to terminate the network also in case of short point to point
connections.
5. If the connection is longer than 1200 m a signal amplifier has to be used.
6. To calculate the time required to scan all the instruments of a network, the following formulae
are to be used:
Trequest
N bit
Baud rate
=
_
*8
Treply
N bit
Baud rate
N char=
°
_
*
sinstrumentNTdelayTSTM °+= *2
N° bit 10 (no parity), 11 (even or odd parity)
N° char 5 + number of Words*2 (function 04), 8 (function 06)
N° word Number of words to be read in the same request
TS Reading execution time
Tdelay1 Minimum time for a new query on the same address
TA Instrument data acquisition time
TM Total network scanning time
N° instruments Number of instruments connected in the network
Tdelay2 Minimum time for a new query on a different address
(23 paginas)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Comentarios a estos manuales