
7.4 SETTING DATA FORMAT AND SPEED
The computer port is set up using internal switch bank 2. The full functions of
these switches are given in appendix 1 together with information on
accessing and identifying these switches.All switches must be set to match
the data transmission set up on the serial port on the host computer and
switch 2:1 must be closed to enable computer port output.
The port can be changed between RS422 and RS485 using internal switch 2
with RS485 selected when the switch is closed.
The communication protocol must be selected between uni-directional and
bi-directional using switch 3 with bi-directional selected when the switch is
closed.
The jumpers on the top circuit board must also be changed if a different
communications standard is used.
JUMPER
RS232 RS422
RS485
J1
C
A
B
J2
B
A
A
J3
B
A
A
If RS422 or RS485 is to be used the plug connecting the socket on the rear
panel to the top circuit board should be moved from P2 to P3. These
connectors are marked on the circuit board.
7.5 UNI-DIRECTIONAL PROTOCOL
As each reading is saved it is automatically sent down the serial port, if the
hardware handshaking line is clear.
7.6 BI-DIRECTIONAL PROTOCOL
As each reading is saved it is stored in an internal buffer, which is battery
backed in case of power failure. When the film weight gauge receives a data
request message from the host computer the data stored in the buffer is sent.
Data Request message:
<40h><01H>where:
<40h>
(1 byte)
ASCII character '@'
<01h>
(1 byte)
When using bi-directional communications, software handshaking is available
as an option as well as hardware handshaking. If selected the XON/XOFF
protocol is used. If XOFF is sent to the film weight gauge it must be followed
by XON before any further transmission will occur.
Содержание SI9500
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