Manual

4–4

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

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.