Siemens S5-100U User Manual page 238

Integrated Blocks and Their Functions
Locating Parameter Errors in "ISTACK"
If the CPU recognizes an error in DB1 in the initial start-up, then the CPU remains in the STOP
mode and stores a message in "ISTACK" describing where the error happened. The "ISTACK"
contains the absolute error address as well as the relative error address
The STEP Address Counter (SAC) in the ISTACK points either to the address that contains the
incorrect input or in front of the address that contains the incorrect input. These are byte
addresses.
Example: Your inputs into DB1 are as follows. The position shaded contains an error.
0: KS = 'DB1 SL1: SLN 40
12: KS = 'DB2
24: KS = ' KBE MB100 KBS MB101
36: KS = 'PGN 1
48: KS = 'CLK DB5
60: KS = 'MW102
72: KS = 'OHE N
84: KS = '12:10:00
96: KS = '01.04. 13:00:00
108: KS = '000000:00:00 # ; SDP: WD';
120: KS = ' 500 ;
132: KS = ' ; END
Figure 9-4. Erroneous Parameter Assignment in DB1
The error causes ISTACK to display the following addresses.
• The absolute (error) address:
• The relative (error) address:
So that you can locate the error in DB1 exactly, you must convert the relative byte address that is
displayed in hexadecimal format into a decimal word address. Decimal format is required because
the programmer displays a DB in words.
000C = 12
H
Hexadecimal Decimal
byte address byte address
The information displayed in the chart above shows that the error occurred after address 0 and
before address 12. In Figure 9-4, argument 40 occupies address 6; the "40" is an incorrect entry
The error is due to a range violation.
9-8
SF ';
DW0 EF DB3 DW0 ';
';
; #CLP: CF 0 ';
DW0 STW ';
STP Y SAV Y ';
SET 4 01.04.92 ';
TIS 4 ';
OHS ';
TFB: OB13 100 ';
';
82F2
000C
12
D
The decimal numbers in front of each input line
represent the word address for the first
character that can be entered for that
respective line. Each word consists of two
characters (2 bytes).
(absolute SAC)
H
(relative SAC)
H
: 2 = 6
D D D
Decimal
word address
S5-100U
.
EWA 4NEB 812 6120-02
.