Rockwell Automation 20-COMM-I Interbus Adapter - Manual (Page 68)

6-6 Using Explicit Messaging (PCP Communications)
The example ladder logic program simplifies addressing the various PCP
indexes. Before calling the PCP Read Subroutine (
Figure 6.3 ), three
registers are loaded to identify the variable to be read:
Table 6.2 PCP Read Main Program Data
The PCP Read Subroutine uses the data in Table 6.2 to create the
following Command Message:
Table 6.3 PCP Read Subroutine Command Message
Table 6.4 PCP Read Subroutine Reply Message
N22:0
The Communication Reference (CR) to read from:
Set to “2” to access Station 1.0 (CR=2)
Set to “3” to access Station 2.0 (CR=3)
N22:1
The desired Parameter / Event / Fault area to be accessed:
Set to “0” to read PowerFlex 70 parameters
Set to “1” to read 20-COMM-I parameters
Set to “2” to read PowerFlex 70 Fault Queue
Set to “3” to read 20-COMM-I Event Queue
N22:2
The actual Parameter number or Event / Fault Queue item
number to read. Set to “1” to read Parameter number 1 or Fault / Event
Queue item number 1....etc....
N22:10 The PCP Command word (set to “4” for PCP Read).
N22:11 The Communication Reference (CR) to read from.
N22:12 The PCP Index of the variable to read (“3001h”= Host parameter 1, etc.).
N22:13 Sub Index not used (set to “0”).
N22:20 = PCP Status Word.
N22:21 = Echo of the Command word (0004h).
N22:22 = Number of words following.
N22:23 = CR.
N22:24 = Result (“0”=good).
N22:25 = Number of bytes read (1-byte for 8-bit Parameters,
2-bytes for 16-bit Parameters, 4-bytes for 32-bit Parameters).
N22:26 = Data Word #1 (1-byte & 2-byte reads, MSW of 4-byte
read).
N22:27 = Data Word #2 (LSW of 4-byte read).
20COMM-UM007A-EN-P.book Page 6 Tuesday, January 22, 2002 10:52 AM