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S5-95F
Table 2-1 gives information about the number and retentive characteristics (the internal memory
contents are retained/are not retained) of these timers, counters, and flags.
Operand
Flags
Counters
Timers
Data Blocks
System Data
*
Individual data words of DB252 to 254 are assigned default values by the operating system
Arithmetic Unit
The arithmetic unit consists of two accumulators, ACCU 1 and 2. The accumulators can process
byte and word operations.
Load
information
from the PII
Figure 2-4. Example of an Arithmetic Logic Unit's Mode of Operation
Accumulator Design
ACCU 1
15
8
7
High
byte
Processor
According to the control program, the processor calls statements in the program memory in
sequence and executes them. It processes the information from the PII and takes into consideration
the values of internal timers and counters as well as the signal states of internal flags.
External I/O Bus
The I/O bus is the electrical connection for all signals that are exchanged between the basic unit
external I/O and the S5-100U modules.
EWA 4NEB 812 6210-02
Table 2-1. Retentive and Non-Retentive Operands
Flags, Counters, Timers, Data Blocks and System Data
Retentive
0.0 to 63.7
0 to 7
1 to 255
Process information
in ACCU 1 and 2
0
Low
Figure 2-5. Accumulator Design
Design, Functions and Operation
*
15
High
Non-retentive
64.0 to 255.7
8 to 127
0 to 127
0 to 255
Transfer
information to
the PIQ
ACCU 2
0
8
7
Low
byte
2-7
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