Liquid Controls SP2200 - Manual (Page 23)

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SERIAL INPUT COMMANDS:
To get a unit on line you must address it by it's device number.
This is done by typing DXX(S), XX= device number. The unit
comes on line and echoes back DEVICE# XX. Insure that
"DEVICE# XX:" is received before requests are sent. The unit
is now ready to receive a command or string of commands
separated by a space. A carriage return (enter) will enter the
commands and processing of requests begins. The carriage
return (Hex Code "D") puts the unit "off line" after data is
processed.
COMMANDS:
EP...........Unit will enter program mode.
DA..........Unit will display (transmit) Count A.
DB..........Unit will display (transmit) Count B.
DC..........Unit will display (transmit) Count C.
EA..........Unit will display (transmit) Rate A.
EB..........Unit will display (transmit) Rate B.
EC..........Unit will display (transmit) Rate C.
KA..........Unit will display K-factor A.
†*KA(S)XXXXX....Unit will load K-factor A
with entered number.
KB..........Unit will display K-factor B
†*KB(S)XXXXX....Unit will load K-factor B
with entered number.
PA...........Unit will display Preset A.
†PA(S)XXXXX....Unit will load Preset A with
entered number.
PB...........Unit will display Preset B
†PB(S)XXXXX....Unit will load Preset B with
entered number.
RA..........Reset Counter A and output
†*RA(S)XXXXXX...Unit will set Counter A to
entered number.
RB..........Reset Counter B and output
†*RB(S)XXXXXX...Unit will reset Counter B to
entered number.
*THE UNIT WILL RECOGNIZE A DECIMAL IF ONE IS
PLACED IN ANY OF THESE DATA VALUES.
†THE UNIT WILL ONLY RECOGNIZE THE LAST FIVE
DIGITS ENTERED (SIX DIGITS FOR RA & RB).
The following is an example of requests and responses:
Transmit from terminal Receive from unit
(s)=Space
D5(s) [Unit #5 Activated] DEVICE# 5:
PA(s)12345(s)PA PA 12345 PA
KA(s)1576(s)KA KA 1576 KA
KB(s)6751(s)KB KB 6751 KB
RA(s)RB[RETURN] RA RB
(UNIT PRESETS AND A & B K-FACTORS ARE SET AND
BOTH COUNTERS ARE RESET)
12345
1576
6751
SERIAL INTERFACE OPERATION:
Data is received and transmitted over standard EIA RS232 or
RS422 levels. Each ten bit character is made up of a start bit,
seven bit ASCII code, a parity bit and a stop bit. Device
number, baud rate, parity and strobe list are entered in the
program setup mode and will remain in memory even if power
is lost.
The input impedance of RS232 is 3K
Ω
to 7K
Ω
worst case. The
terminal addressing the unit must be capable of driving all
loads in the loop. The input impedance of RS422 is much
higher and there should be no problem driving as many as 99
units. The transmit line remains in a high impedance "off"
state until addressed. Only one unit is to be on line at a time!!!
More than one unit on line could damage the unit or destroy
the transmitted data.
When the unit is active (on line) it will operate in a full duplex,
echo back mode, so that data sent from the terminal will be
transmitted back for verification. When the unit is "on line",
use the proper serial transmit commands to request data or
set a new value. Up to 80 characters of data can be linked
together and transmitted to the unit in a string as long as there
is a space between the commands. If an error is made, a
correction can be made by back spacing and retyping correct
data before the return (enter) is sent. Once a return (enter) is
sent, the unit begins processing the data and will transmit the
requested data on a non-priority basis over the data transmit
line. A keypad entry or incoming data will halt the data
communication cycle. Therefore, there should be a pause
after data is requested to insure that all data has been
transmitted before making another request or addressing
another unit. If the unit is not busy, it should not take longer
than 300 msec to process each request. To find the cycle time
to process and transmit a request, calculate the bit transmit
time by using this formula: [(1
÷
baud rate) x (80) + .005] x
number of requests made. This time will be extended if the
unit must service the front keypad. If transmission has not
started within two seconds after data is requested, it can be
assumed that there is a problem. The unit transmits a carriage
return and line feed after each data value. Any new commu-
nication must be started with DXX(S) (device number and
space).
RS232/RS422 - IBM-PC INTERFACE:
The following program is for IBM basic to set up RS232/RS422
on serial port (#1) at 300 baud. Run this program after
connecting the serial interface connections.
10 SCREEN 0,0:WIDTH 80
20 CLS:CLOSE
30 OPEN "COM1:300,n,7,1,CS,DS,CD" AS #1
40 ON ERROR GOTO 110
50 B$=INKEY$
60 IF B$< >"" THEN PRINT #1,B$;
70 IF EOF (1) THEN 50
80 A$=INPUT$ (LOC(1),#1)
90 PRINT A$;
100 GOTO 50
110 RESUME