Rockwell Automation RECOMM-IBUS Interbus Communications Module - Manual (Page 66)

7-6 Interbus Communications Module
The sample ladder logic program simplifies addressing the various
PCP indexes. Before calling the PCP Read Subroutine (figure 7.9),
three registers are loaded to identify the variable to be read:
The PCP Read Subroutine uses the data in table 7.5 to create the
following Command Message (table 7.6):
Table 7.5 – PCP Read Main Program Data
Register Description
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 SP600 parameters
Set to “1” to read RECOMM-IBUS parameters
Set to “2” to read SP600 Fault Queue
Set to “3” to read RECOMM-IBUS 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....
Table 7.6 – PCP Read Subroutine Command Message
Register Description
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”).
Table 7.7 – PCP Read Subroutine Reply Message
Register Description
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).