Siemens Simatic S7 Series System Manual

Special memory (SM) and system symbol names
D.6 SMB4: Interrupt queue overflow, run-time program error, interrupts enabled, freeport transmitter idle, and
value forced
S7-200 SMART
670 System Manual, 09/2015, A5E03822230-AC
D.6
SMB4: Interrupt queue overflow, run-time program error, interrupts
enabled, freeport transmitter idle, and value forced
Special memory byte 4 (SM4.0 - SM4.7) contains the interrupt queue overflow bits and a bit
(SM 4.4) that shows whether interrupts are enabled or disabled. These bits indicate either
that interrupts are occurring at a rate greater than can be processed or that interrupts were
disabled with the global interrupt disable instruction.
Other bits indicate:
● A run-time program error
● Freeport transmitter status
● If any PLC memory value is currently forced.
Table D- 5 SMB4 system status
S7-200 SMART
symbol name
SM address
Description
Comm_Int_Ovr
** SM4.0
1 = Communication interrupt queue has overflowed.
Input_Int_Ovr ** SM4.1 1 = Input interrupt queue has overflowed.
Timed_Int_Ovr
** SM4.2
1 = Timed interrupt queue has overflowed.
RUN_Err
SM4.3
1 = Run-time programming non-fatal error is detected.
Int_Enable
SM4.4
1 = Interrupts are enabled.
Xmit0_Idle
SM4.5
1 = Port 0 transmitter is idle (0=transmission in progress).
Xmit1_Idle
SM4.6
1 = Port 1 transmitter is idle (0=transmission in progress).
Force_On
SM4.7
1 = Any memory location is forced.
** Use status bits 4.0, 4.1, and 4.2 only inside an interrupt routine. These status bits are reset when the queue is emptied,
and control is returned to the main program.
D.7
SMB5: I/O error status
Special Memory Byte 5 (SM5.0 - SM5.7) contains status bits which indicate error conditions
that were detected in the I/O system. These bits provide an overview of the I/O errors
detected.
Table D- 6 SMB5 I/O error status
S7-200 SMART
symbol name
SM address
Description
IO_Err
SM5.0
This bit is set ON if any I/O errors are present.

Siemens Simatic S7 Series Specifications

General

CPU	Varies by model (e.g., S7-300, S7-400, S7-1200, S7-1500)
Communication Interfaces	PROFIBUS, PROFINET, Ethernet, MPI
Programming	TIA Portal, STEP 7
Programming Languages	LAD, FBD, STL, SCL, GRAPH
I/O Modules	Digital, Analog, Specialty modules available
Operating Temperature	0°C to 60°C (standard models)
Mounting	DIN rail mounting
Operating Voltage	24V DC or 120/230V AC (varies by model)
Protection Class	IP20 (standard models)
Memory	Varies depending on the S7 model. Includes work memory (RAM) for program execution, load memory (EEPROM or Flash) for program storage, and system memory for operating system functions. Memory sizes range from kilobytes to megabytes.