Msg instruction control block – Rockwell Automation 1747-L55x,D174710.4 SLC 500 Ethernet User Manual
Page 34
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Communicating on the Ethernet Network
Publication 1747-10.4
MSG Instruction Control Block
The following are MSG control blocks, without and with logical
ASCII addressing. The length of the control block without logical
ASCII addressing is 51 words. With logical ASCII addressing, the
length of the control block is 93 words.
SLC 5/05 Channel 1 (Ethernet port)
MSG Control Block without Logical ASCII Addressing
WORD
15
14
13
12
11
10
09
08
07
06
05
04
03
02
01
00
0
EN
ST
DN
ER
CO
EW
NR
TO
Error Code
1
Reserved (Target Node Not Used)
2
Number of Elements
3
Not Used
4
File Type (based on local source or destination address)
5
Not Used
6
Not Used
7
Reserved (Internal Messaging Bits)
WQ
8
Message Timer Preset
9
Message Timer Scaled Zero
10
Message Timer Accumulator
11
Data Length in Bytes
12
AO=0
Reserved (Internal Messaging Bits)
Reserved
13
Reserved
14
First Byte of IP Address String
➀
Second Byte of IP Address String
15
Third Byte of IP Address String
…
…
…
…
…
34
Forty-First Byte of IP Address String
NULL Byte of Longest IP Address String
35
Reserved
Reserved (Ethernet Message Type); must be 0
36–50
Reserved for Future Use
➀
The IP Address string format is up to 42 ASCII characters including a terminating NULL character. The first byte in the array is the
left-most character in the string as written. For example: If the IP Address is 423.156.78.012, the first byte is the ASCII character “4”. If
the MSG destination is an INTERCHANGE client on a host computer, the destination is specified as “client” and stored as a NULL
terminated string.