Siemens SIMATIC S7 - SMB1: Instruction Execution Status

Special memory (SM) and system symbol names
D.3 SMB1: Instruction execution status
S7-200 SMART
System Manual, V2.3, 07/2017, A5E03822230-AF
803
D.3
SMB1: Instruction execution status
Special memory byte 1 (SM1.0 - SM1.7) provides execution status for various instructions,
such as table and math operations. These bits are set and reset by instructions at execution
time.
Table D- 2 SMB1 instruction execution status bits
S7-200 SMART
symbol name
SM address
Description
Result_0
SM1.0
Certain instructions set this bit to TRUE when the result of the operation is zero.
Overflow_Illegal SM1.1 Certain instructions set this bit to TRUE when either an overflow results or when
the instruction detects an illegal number value.
Neg_Result
SM1.2
Math operations set this bit TRUE when the operation produces a negative result.
Divide_By_0 SM1.3 The CPU sets this bit TRUE when the program attempts a division by zero.
Table_Overflow SM1.4 The Add to Table (ATT) instruction sets this bit TRUE when the referenced data
table is full.
Table_Empty SM1.5 The CPU sets this bit TRUE when either LIFO or FIFO instructions attempt to read
from an empty table.
Not_BCD SM1.6 The CPU sets this bit TRUE for an illegal value (non-BCD) in a BCD to binary con-
version.
Not_Hex SM1.7 The CPU sets this bit TRUE for an illegal value (non-hex ASCII digit) during ASCII
to Hex (ATH) conversion.