Liquid Controls SP2800 User Manual

Page 47

8-9 Strobe Wiring

8-9.1 RS232 Strobe Wiring (RS232, 25 Pin
Connector)
The 3 data lines are hooked up to Pins 9, 10,
and 11. These lines must be held high while
a strobe of at least 25 milliseconds is given on
Pin 18. Data is transmitted in RS232 serial
format on the Transmit Data Line (Pin 3).

a) Pin 9, Binary 1's Input
b) Pin 10, Binary 2's Input
c) Pin 11, Binary 4's Input
d) Pin 18, Strobe Input
e) Pin 3, Transmit Data
f) Pin 7, Signal Ground for Reference

Refer to 8-5.1 Wiring Hookup RS232 / Strobe
(25 Pin Connector) for diagram.

8-9.2 RS422 Strobe Wiring (RS422, 37 Pin
Connector)
The 3 data lines are hooked up to Pins 9, 10,
and 11. These lines must be held high while
a strobe of at least 25 milliseconds is given on
Pin 3. Data is transmitted in RS422 format on
the Transmit Data Line (Pins 6, 24).

a) Pin 21, Binary 1's Input
b) Pin 14, Binary 2's Input
c) Pin 10, Binary 4's Input
d) Pin 3, Strobe Input
e) Pins 6, 24, Transmit Data
f) Pins 19, 20, Signal Ground for Refer-

ence

Refer to 8-7.1 Wiring Hookup RS422 / Strobe
(37 Pin Connector) for diagram.

8-10 Serial Interface Operation
Data is received and transmitted over stan-
dard EIA RS232 or RS422 levels. To ad-
dress a Batcher unit, transmit a "D" (device)
followed by the 1 to 15 code number and a
"Space". Once the space has been re-
ceived the Batcher becomes active and re-
sponds back, "Device XX:" (Device number).
(Once active, the unit works in a full duplex
echo back mode, so that data sent from the
terminal will be transmitted back for verifica-
tion.) Once the unit is "on line", use the

proper serial transmit codes to request data or
set a new value. (See Section 8-10.2
RS232/RS422 Serial Input Codes). Up to 80
characters of data may be linked together and
transmitted to the Batcher (as long as there is
a space between the different codes). If an
error is made, a correction can be made by
back spacing and retyping correct data before
the "Carriage Return" (Enter) is sent. Once
"Carriage Return" (Enter) is sent, the Batcher
starts processing the data and will transmit
the requested data on a non-priority basis
over the data transmit line. A Batcher keypad
entry or incoming data will halt the data com-
munication cycle. Therefore, there should be
a pause after data is requested to insure that
all data has been transmitted before another
unit is addressed and brought on line. When
transmitting, the Batcher will precede each
data value with a "Carriage Return" and "Line
Feed" code and answer only with requested
data in the order the requests were made.
After all requested data has been transmitted
any new communication must be started
again by DXX (Device number) and space.

8-10.1 Serial Communications Timing.
If the Batcher is not busy, it should not require
more than 5 msec to process each request.
To find the cycle time to process and transmit
a request, calculate the bit transmit time by
dividing 1 by the baud rate; multiply that by 80
(8 characters each; 10 bits per character);
add 5 msec. to this product and multiply by
the number of requests made. Example:
Typical time to transmit 1 uninterrupted re-
quest at 300 baud rate is .272 sec = (1

300) x

(80) + 0.005. This time will be extended if the
Batcher must service the front keypad or one
of the inputs. In practice, if transmission has
not started within 2 seconds after data is re-
quested, it can be assumed that there is a
problem.