User guide

Hardware
22
890 USE 108 00 August 2001
Secured Data
Area (SDA)
(E984-258/265/
275/285 Only)
This feature allows you to configure an area in RAM that is secured from being
overwritten. Secured Data Area (SDA) is a block of the Compact PLCs RAM that is
set aside as 6x data space. The SDA can only be written to by specific functions that
require secured data storage (Gas Flow Calculation Audit Trails, etc.). General
purpose Modbus commands, built-ins, and loadables can NOT write to the SDA.
Modbus Read (function 20) is able to read from the SDA, Modbus Write (function
21) is NOT able to write to the SDA. The SDA size range is 0 ... 128K words using
ONLY 1K word blocks. From the main Concept menu, select Configure, then RTU
Extension. The RTU-Specific Parameters dialog box appears. Enter the size you
require. Then confirm with OK. Refer to the applicable user manual for the specific
function for the required SDA size. For example, for Gas Flow, refer to the Starling
Associates Gas Flow Loadable Function Block User Guide (890 USE 137 00).
Time Synchroni-
zation of the TOD
(E984-258/265/
275/285 Only)
This feature allows you to synchronize your PLCs Time-Of-Day (TOD) clock time
signal from GPS (Global Positioning System) satellites. This feature provides
accurate time stamping of logged data, and the synchronization of different PLCs
because the time synchronization is dependent on the scan of the PLC, the
accuracy is +/-10ms. Connect the 470 GPS 001 00 GPS Receiver to the PLCs
Interrupt Connections located on the front of your PLC. Refer to the User Information
shipped with the GPS module (Part Number 708874.21) and below. To see when
the time synchronize is present or not refer to bit 13 of word 1 (CPU-Status) of the
STAT Block. (See Word 182 - Health Status, p. 207). A 1 indicates you have a valid
signal and the TOD has been updated, a 0 indicates you are NOT receiving a time
signal. Connecting the GPS module to your PLC is very easy.
This is how to wire up the GPS module.
470 GPS 001 00 Receiver E984-258/265/275/285
1 2 3
IN
M
PLC Interrupt
Connection
+24Vdc
GND