Technical equipment of TC600 PLC
11
TXV 138 08.02
Memory of CPU parameters is power-independent memory designed for
storage of parameters that can be set in the PLC SET mode. Contents of
the memory remain retained even when the PLC power supply is turned off
or if the battery is discharged.
The scratchpad memory is a part of the CPU RAM memory accessible to
the user in the form of input images (registers X), outputs images (registers
Y), system (S) and user registers (R). Preserving of the scratchpad contents
after turning off of the PLC power supply and restarts is program-controlled.
The behaviour is described in detail in Chapter 10.
The DataBox is an optional complement of the CPU, fitted by the pro-
ducer on the basis of an order. It extends the user accessible RAM memory
by 128kB or the data memory by 512kB. When the PLC is turned off, the
memory is supplied from a built-in lithium battery. It is designed for working
with greater amounts of data, for example for archiving of data on the con-
trolled process for a longer time period etc. The data can be written to the
memory or read, respectively, either by using the PLC user program or
through the serial line.
For support of the DataBox program attendance, there are three user in-
structions available. The READDBX instruction is intended for reading of
data from DataBox into R registers, the WRITEDBX instruction is intended
for writing of data from R registers to the DataBox, and the SIZEDBX in-
struction serves for identification of the DataBox size. Detailed description
of function of instructions, their definitions, structures of the parameters
zone for instructions READDBX and WRITEDBX and way of calling of in-
structions in the user program are given on the distribution diskette xPRO
which forms a part of the PLC delivery.
For serial communication with the DataBox, either CH1 can be used
which always operates in the PC mode or channels CH2, CH3 set in the PC
mode. To support serial communication with the DataBox, the
COMPLC.EXE program is available which allows for reading data from Da-
taBox into a file or write data from a file to DataBox, respectively, and test
size of memory accessible in the form of the DataBox. Working with the
DataBox is possible starting from the COMPLC.EXE program version 1.6.
The program, which is found on the xPRO distribution diskette, must be run
under the MS DOS operating system.
When the PLC power is turned off, the RAM memory and RTC circuit are
supplied from a built-in lithium battery. Parameters of the used battery allow
for backup with the power supply turned off for the minimum time of 20000
hours. In common operating conditions (operating temperature of 20 °C,
unidirectional operation at least) and typical power take-off of the backing
circuits, the backup time is limited by battery life (5 years at the minimum).
Voltage of the backup battery is evaluated by the diagnostic system. In
the case the voltage drops under 2.5 V, bit .0 of the S35 system register is
set to the state log. 1. PLC continues with its activity until the voltage drops
under the minimum supply voltage of the RTC circuit. Evaluation of the
RTC circuit failure leads to bringing the PLC in the HALT mode and an-
nouncing the error message 80 0C 00 00.
Memory of CPU
parameters
Scratchpad memory
The DataBox
Support of working
with the DataBox
Backup of the RAM
memory and RTC
circuit power supply
Detection of state of
the backup battery
