Rockwell Automation 1747-PT1, D1747NP002 Hand-Held Terminal - Manual (Page 396)

Chapter 27
The Status File
27–28
Address Description 5/02
5/01,
Fixed
S:20
and
S:21
Test – Fault/Powerdown – Rung/File
Read/write. These registers indicate the executable rung (word S:20)
and file (word S:21) number that the processor last executed before a
major error or powerdown occurred. To enable this feature, you must
select the Test Single Step option at the time you save your program.
You can use these registers to pinpoint the execution point of the
processor at the last powerdown or fault routine entry. This function
is also active in the Run mode. See S:2/4.
Application example: Your program contains several TON
instructions. TON T4:6 in file 2, rung 25 occasionally obtains a
negative preset. Recovery from the negative preset fault is possible
by placing the preset at 100 and resetting the timer.
Place the following rung in your fault routine to accomplish this. Bit
B3/0 is latched as evidence that an application recovery has been
initiated.
Note: The HHT can save a SLC 5/02 program that has this option
enabled, but the Test Single Step mode is not available with the HHT.
•
MOV
MOVE
Source
100
Dest T4:6.PRE
EQU
EQUAL
Source A
S:6
Source B 52
(RET)
(RES)
T4:6
(L)
B3
0
(U)
S:1
13
File Number The value 52 equals 0034 Hex. This is
the error code for a negative timer
preset.
EQU
EQUAL
Source A
S:20
Source B 25
EQU
EQUAL
Source A
S:21
Source B 2
Rung Number