User Manual, PRIOR to Firmware rev. 3.0 Owner manual

Publication 1404-UM001D-EN-E - October 2004

4-32 Communications

In the SLC 500 and PLC-5, you assemble the explicit message header

in an integer file and transfer it to the scanner module. When the

response is received, you transfer the response from the scanner to

another integer file. The message header consists of 6 words

organized as follows:

Word 0 contains a transmit identifier (TXID) and command byte.

Assign each explicit message a unique TXID in the range of 0 to 255

decimal (0 to FF hex). The TXID is used to identify the response to

this message request. Valid command codes are:

• 1 hex = Execute transaction block. Use this command first to

start the explicit message.

• 4 hex = Delete transaction from response queue. Use this

command after you copy the response from the scanner to

remove the response from the scanner and enable further

explicit messages.

Word 1 contains the DeviceNet scanner port number and the

transaction body size in bytes. The SLC 500 scanner uses only port 0; a

PLC-5 DeviceNet scanner has two ports, 0 and 1. For a read request,

the transaction body size is 3 words (see table above) therefore 6

bytes. For a write, the body size is the data size in bytes plus the

6-byte path (class/instance/attribute).

Word 2 contains the DeviceNet service code and the MAC ID or node

number of the server device, in this case, the Powermonitor 3000.

Valid service codes for use on Class 4 assembly instances are:

Table 4.6

Message Word High byte Low byte

Header 0 Transmit ID Command

1Port Size

2 Service MAC ID

Body 3 Class

4Instance

5 Attribute

6 Data to write if applicable

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