DayTronic 3500 Series, Инструкция по эксплуатации

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As noted in Section 3.a.4, the maximum baud rate at which network inter-
changes can take place will depend on
• the capacity of the supervisory computer's input buffer;
• the actual network setup configuration; and
• the efficiency of the computer's data-input routine.
Since there is no hardware handshake, it is necessary that the computer be
equipped with an input buffer capable of receiving the entire answer to each and
every network interrogation at the desired baud rate, without interruption.
To prevent buffer overruns under conditions of peak loading—where, for exam-
ple, the computer program requires frequent writing of data to disk, or where
"Terminate and Stay Resident" programs attach to the timer interrupts—care
must be taken in setting up the program for requesting data from the network.
See the sample GW-BASIC inputting routine given below.
To ensure proper network communications, you should always
1. Assign a unique node number to each network node.
2. Make sure that every OPEN (OPN) command observes the proper syntax.
See Section 5.a.3 and Line 3030 of the GW-BASIC program below.
3. Set all network nodes to the same baud rate, number of data bits, and parity
setting.
4. Set all network nodes to 2 stop bits.
To maximize network speed, you should also observe the following rule:
5. For each network node, the COMMAND TERMINATOR ("CMT") and END-OF-
TRANSMISSION TERMINATOR ("EOT") should both be set to
CARRIAGE
RETURN (= hexadecimal [0D]).
S
AMPLE
P
ROGRAM
100 '-----------------------------------------------------------
110 TERM$=CHR$(13) 'Terminator is carriage return.
120 TIMEOUT%=1!
'Timeout is 1 second.
130 OPEN "COM1:9600,N,8,2,CS,DS" AS #1
132 INPUT "Is this a network (RS 485) or a single (RS 232) device?
(N/S) ";ANS$
134 IF ANS$ = "S" OR ANS$ = "s" GOTO 170 'Bypass opening a node.
136 IF ANS$ <> "N" AND ANS$ <> "n" GO TO 132 'Ask again.
140 INPUT "Enter Node Number ";NODE%
150 GOSUB 3000
'Open node
160 IF ERRCODE% = 2 THEN PRINT "Unable to open node"NODE% : GOTO 250
D.1
N
ETWORKING
G
UIDELINES
D
N
ETWORKING
G
UIDELINES
Appendix D
Networking Guidelines