Allen-Bradley PowerFlex 20-COMM-P, User Manual, Page: 81 / 117

Using Explicit Messaging (Parameter Protocol) 6-11
Figure 6.5 Example SLC Ladder Logic - Station 1 Parameter Protocol
SLC Ladder Example - Station 1 Parameter Protocol
This circuit utilizes the Parameter Protocol. A REQUEST to Station 1 is processed only one at a time, and after each
RESPONSE from Station 1 a zero must be sent and received to 'handshake' before the next REQUEST/RESPONSE transaction
can take place. For example:
Send a parameter read request --> Receive a parameter read response --> Send a "0" --> Receive a "0" --> [Transaction complete]
If the RESPONSE PCA Word 1 (N10:10) is "0", then a REQUEST can be initiated.
Elsewhere in the user program these words must be loaded with message data prior to initiating the REQUEST:
N7:10 = RC = the operation to be performed ("1"=Read, "2" = 16-bit Write, "3" = 32-bit Write)
N7:11 = PNU = the parameter number to read or write
N7:12 = Subindex = the DPI port # ("0"= Host or PowerFlex drive, "5" = 20-COMM-P, etc.)
N7:13 = PVA #1 = the parameter value (high word) - only used when writing parameters
N7:14 = PVA #2 = the parameter value (low word) - only used when writing parameters
The four Parameter Protocol Words set up in the scanner are used to perform the Parameter Protocol:
N20:10 = contains RC (the operation to be performed) and PNU (the parameter number to read or write) combined
N20:11 = Subindex (the DPI port #)
N20:12 = PVA #1 (the parameter value (high word))
N10:13 = PVA #2 (the parameter value (low word))
B3:19/15 is turned ON elsewhere in the program after the REQUEST message (N7:10-14) is loaded. This causes one Parameter
Protocol read or write to occur and B3:19/15 is turned OFF when the transaction is complete.
0016
B3:19
15
Station 1
Par Prot
Messaging
Request
EQU
Equal
Source A
N10:10
0<
Source B
0
0<
EQU
Station 1
RESPONSE
PCA Word
MOV
Move
Source
N7:11
15<
Dest
N20:10
0<
MOV
Station 1
PCA Word
N7:10
0
RC bit 0
L
N20:10
12
PCA Word
RC
bit 0
N7:10
1
RC bit 1
L
N20:10
13
PCA Word
RC
bit 1
COP
Copy File
Source
#N7:12
Dest #N20:11
Length 3
COP
IND Word
(Subindex)
This section of the routine is only needed if the application needs to perform Parameter Protocol Reads or Writes to Station 1.
On power-up, initialize the Parameter Protocol routine.
0015
S:1
15
First Pass
U
B3:19
15
Station 1
Par Prot
Messaging
Request
20COMM-UM006A-EN-P.book Page 11 Friday, September 28, 2001 10:43 AM