Rockwell Automation 1771-DA,D17716.5.13 U MNL 1771-DA ASCII I/O MODULE User Manual
Page 87
ASCII I/O Module Tutorial
Chapter 4
4Ć13
Table 3.G
Transfer of Balance of String
POSITION
FILE DATA
ASCII Equivalent
001
002
003
004
005
006
007
008
009
010
E011
0000
2020
2020
3637
3839
3041
4243
4445
4647
6 7
8 9
0 A
B C
D E
F G
Your program must include instructions for processing new data read
from the module. If not, data in your read block transfer file will be
written over in the next read block transfer.
You can do this by examining whether status word two (SW2) contains
data, using a greater-than instruction. When the value in SW2 is greater
than zero (new data flag), move new read block transfer data to an
alternate storage file. Your program can process it before it is overwritten
by the next transfer of new data (Figure 3.3). Make the address of the
source file of the file-to-file move instruction (file A) the same address as
the read block transfer file. Also examine the BTR done bit.
Figure 3.3
Example Programming, New Data Flag
Bit
17
BLOCK XFER READ
DATA ADDR:
MODULE ADDR:
BLOCK LENGTH:
FILE:
030
111
16
252 - 271
EN
011
17
DN
111
17
Bit
FILE TO FILE MOVE
COUNTER ADDR:
POSITION:
FILE LENGTH:
FILE A:
FILE R:
RATE PER SCAN:
035
001
16
254 - 271
16
EN
035
17
DN
035
15
035
00
SW2>0
253
<
BT Done
Storage
Bit
327
G
000
Storage
111