
RS232 Communications
RS485 Communications
LD METER (DTE)
1
TXD
RXD
RECEIVING DEVICE
DB25 DB25 DB9
DCE DTE DTE
2 3 2
The RS485 communication standard allows the connection of up to 32
devices on a single pair of wires, distances up to 4,000 ft. and data rates as high
as 10M baud (the LD is limited to 38.4k baud). The same pair of wires is used
to both transmit and receive data. RS485 is therefore always half-duplex, that is,
2
RXD
TXD
3
2
3
data cannot be received and transmitted simultaneously.
3
COMM.
5
7
5
LD METER
+5V
RECEIVING DEVICE
Terminal Block Connection Figure
Transmit
Enable
47K
5
B (-)
RS232 is intended to allow two devices to communicate over distances up to
50 feet. Data Terminal Equipment (DTE) transmits data on the Transmitted Data
(TXD) line and receives data on the Received Data (RXD) line. Data Computer
47K
4
A (+)
Equipment (DCE) receives data on the TXD line and transmits data on the RXD
line. The LD emulates a DTE. If the other device connected to the meter also
emulates a DTE, the TXD and RXD lines must be interchanged for
communications to take place. This is known as a null modem connection. Most
printers emulate a DCE device while most computers emulate a DTE device.
Some devices cannot accept more than two or three characters in succession
3
COMM.*
without a pause in between. In these cases, the meter employs a busy function.
As the meter begins to transmit data, the RXD line (RS232) is monitored to
* OPTIONAL
Terminal Block Connection Figure
determine if the receiving device is “busy”. The receiving device asserts that it
is busy by setting the RXD line to a space condition (logic 0). The meter then
suspends transmission until the RXD line is released by the receiving device.
Sections 4 and 5 apply to Programmable Models Only
4.0 R EVIEWING THE F RONT P ANEL K EYS AND D ISPLAY
KEY
PAR
SEL ?
RST ?
DISPLAY MODE OPERATION
Access Programming Mode
Index display through selected displays
Resets count display(s) and/or outputs
PROGRAMMING MODE OPERATION
Store selected parameter and index to next parameter
Advance through selection list/select digit position in
parameter value
Increment selected digit position of parameter value
OPERATING MODE DISPLAY DESIGNATORS
“ ? ” - To the left of the display is the rate value.
- Counter A has no designator.
“ 1 ” - To the right of digit 6 indicates setpoint 1 output status.
“ 2 ” - To the right of digit 1 indicates setpoint 2 output status.
“ ? ” - To the left of the display is the Counter B value (dual count or batch).
Pressing the SEL ? key toggles the meter through the selected displays. If display scroll is enabled, the display will toggle automatically every four seconds
between the rate and count values.
5.0 P ROGRAMMING
THE
M ETER
DISPLAY
MODE
PAR
NO
OVERVIEW
PROGRAMMING MENU
Display and Front
Setpoint
Serial
Input Setup
Rate Setup
Panel Key
Output
Setup
Pro
Parameters
SEL
PAR
1-INP
Parameters
PAR
2-rAtE
Parameters
PAR
3-dSP
Parameters
PAR
4-SPt
Parameters
PAR
5-SEr
PROGRAMMING MODE ENTRY (PAR KEY)
It is recommended all programming changes be made off line, or before
installation. The meter normally operates in the Display Mode. No parameters
can be programmed in this mode. The Programming Mode is entered by
pressing the PAR key. If it is not accessible, then it is locked by either a security
code or a hardware lock.
6
MODULE ENTRY (SEL ? & PAR KEYS)
The Programming Menu is organized into five modules. These modules group
together parameters that are related in function. The display will alternate between
??? and the present module. The SEL ? key is used to select the desired module.
The displayed module is entered by pressing the PAR key.