Memory Parameters - Emerson PACSystems RX3i User Manual

PACSystems™ RX3i and RSTi-EP CPU Reference Manual
GFK-2222AK
Scan Parameters
Number of Last (Available
Scans The number of scans to execute after the PACSystems CPU receives an indication that
a transition from RUN Mode to STOP Mode should occur. (Used for STOP and STOP-
Fault, but not STOP-Halt.)
Choices: 0, 1, 2, 3, 4, 5.
Default:
3.2.6

Memory Parameters

The PACSystems user memory contains the application program, hardware configuration
(HWC), registers (%R), bulk memory (%W), analog inputs (%AI), analog outputs (%AQ),
and managed memory.
Managed memory consists of allocations for symbolic variables and I/O variables. The
symbolic variables feature allows you to create variables without having to manually
locate them in memory. An I/O variable is a symbolic variable that is mapped to the inputs
and outputs of a module in the hardware configuration. For details on using symbolic
variables and I/O variables, refer to PACSystems RX3i and RSTi-EP CPU Programmer's
Reference Manual, GFK-2950 Section 4.
The amount of memory allocated to the application program and hardware configuration
is automatically determined by the actual program (including logic C data, and %L and
%P), hardware configuration (including EGD and AUP), and symbolic variables created in
the programming software. The rest of the user memory can be configured to suit the
application. For example, an application may have a relatively large program that uses
only a small amount of register and analog memory. Similarly, there might be a small
logic program but a larger amount of memory needed for registers and analog inputs and
outputs. Note that the content of reference memory is cleared any time the size of
reference memory is changed.
A-4 provides a summary of items that count against user memory.
3.2.6.1 Calculation of Memory Required for Managed Memory
The total number of bytes required for symbolic and I/O variables is calculated as follows:
[((number of symbolic discrete bits) × 3) / (8 bits/byte)]
+
+
+
CPU Configuration
only for CPUs
0 when creating a new PACSystems target.
0 when converting a Series 90-70 target to a PACSystems target.
1 when converting a Series 90-30 target to a PACSystems target.
[((number of I/O discrete bits) × Md) / (8 bits/byte)]
[(number of symbolic words × (2 bytes/word)]
[(number of I/O words) × (Mw bytes/word)]
with firmware version
Section 3
October 2019
1.5 and greater.)
57