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Chapter 7. Programming SRTP Channel Commands
114 PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual GFK-2224Q
The COMMREQ Command Block: General Description
When the COMMREQ function is initiated, the Command Block is sent from the PLC CPU to the Ethernet
Interface. The Command Block contains the details of a Channel command to be performed by the Interface.
The address in CPU memory of the Command Block is specified by the IN input of the COMMREQ Function
Block. It can be any valid address within a word-oriented area of memory (%R, %AI, %AQ, %P, %L, or %W). The
Command Block is set up using an appropriate programming instruction, such as a BLOCK MOVE or DATA INIT
COMM). The Command Block has the following structure:
Word 1 Data Block Length (words)
Word 2 WAIT/NOWAIT Flag
Word 3 COMMREQ status word Memory Type
Word 4 COMMREQ status word Address Offset
Word 5 Reserved
Word 6 Reserved
Words 7 and up Data Block (Channel Command Details)
(Word 1) Data Block Length : This is the length in words of the Data Block portion of the Command Block. The
Data Block portion starts at Word 7 of the Command Block. The length is measured from the beginning of the
Data Block at Word 7, not from the beginning of the Command Block. The correct value for each command,
and the associated length of each command, is specified in the next section.
(Word 2) WAIT/NOWAIT Flag: Must be set to zero for TCP/IP Ethernet Communications.
COMMREQ Status Word : The Ethernet Interface updates the COMMREQ status word to show success or failure
of the command. Command words 3 and 4 specify the PLC memory location of the COMMREQ status word.
(COMMREQ Status Word values are described in Chapter 12.)
(Word 3) COMMREQ Status Word Memory Type: This word specifies the memory type for the COMMREQ
status word. The memory types are listed in the table below:
Type Value
(Decimal)
Value
(Hex.)
Description
%R 8 08H Register memory (word mode)
%AI 10 0AH Analog input memory (word mode)
%AQ 12 0CH Analog output memory (word mode)
%I 16
70
10H
46H
Discrete input memory (byte mode)
Discrete input memory (bit mode)
%Q 18
72
12H
48H
Discrete output memory (byte mode)
Discrete output memory (bit mode)
%T 20
74
14H
4AH
Discrete temporary memory (byte mode)
Discrete temporary memory (bit mode)
%M 22
76
16H
4CH
Discrete momentary internal memory (byte mode)
Discrete momentary internal memory (bit mode)
%G 56
86
38H
56H
Discrete global data table (byte mode)
Discrete global data table (bit mode)
%W 196 C4H Word memory (word mode; limited to %W1 through %W65536)
(Word 4) COMMREQ Status Word Address Offset: This word contains the offset within the memory type
selected. The status word address offset is a zero-based number. For example, if you want %R1 as the
location of the COMMREQ status word, you must specify a zero for the offset. The offset for %R100 would be
99 decimal. Note, however, that this is the only zero-based field in the Channel commands. (When using %W
memory, the maximum offset value that can be entered is 65535, signifying %W65536.)
(Word 5): Reserved. Set to zero.
(Word 6): Reserved. Set to zero.
(Words 7 and up) Data Block : The Data Block defines the Channel command to be performed.