Smb1: Instruction Execution Status - Siemens SIMATIC S7 System Manual

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