S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
799
Special memory (SM) and system symbol names
SM (Special Memory) overview
The S7-200 SMART CPU provides special memory that contains system data. SMW is the
prefix that indicates a special memory word. SMB is the prefix that indicates a special
memory byte. You address individual bits as SM<byte number>.<bit number>. The System
Symbol table in STEP 7-Micro/WIN SMART displays the special memory.
SMB0 to SMB29, SMB480 to SMB515, and SMB1000 to SMB1699 (S7-200 SMART read-only
special memory)
-200 SMART
CPU writes new changes to the system data stored
in special memory.
Read system status
from the CPU
SMB0 to SMB29, SMB480 to SMB515, and SMB1000 to SMB1699 are
read
-only from your program. If a program includes logic to write to a
-only SM address, STEP 7-Micro/WIN SMART compiles the pro-
gram without error. The CPU program compiler, however, will reject the
program and display "Operand range error, Download failed".
Your program can read data stored in special memory addresses, eva
l-
uate the current system status, and use conditional logic to decide how
to respond. In run mode, the continuous scanning of your program logic
provides continuous monitoring of system data.
● SMB0 (Page 802) System status bits
● SMB1 (Page 803) Instruction execution status bits
● SMB2 (Page 804) Freeport receive character
● SMB3 (Page 804) Freeport parity error
● SMB4 (Page 805) Interrupt queue overflow, run-time program error, interrupts enabled,
freeport transmitter idle, and forced value
● SMB5 (Page 805) I/O error status bits
● SMB6-SMB7 (Page 806) CPU ID, error status, and digital I/O points
● SMB8-SMB19 (Page 807) I/O module ID and errors
● SMW22-SMW26 (Page 808) Scan times
● SMB28-SMB29 (Page 808) Signal board ID and errors
● SMB480-SMB515 (Page 823) Data log status (read only)
● SMB1000-SMB1049 (Page 826) CPU hardware/firmware ID
● SMB1050-SMB1099 (Page 826) SB (signal board) hardware/firmware ID
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