Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Instrukcja Użytkownika Pobierz pdf (Strona 237)

14–5Line Monitor Examples

Publication

17706.5.16 - October 1996

Field Value Function

DLE STX (2 bytes) 10 02 Indicates the start of the reply message

DST (destination) 0A Indicates the node address that the reply is being sent back to. In our example command message,

the 1770KF2 put its address in the source (SRC) byte before sending the command message to the

1771KA2. The 1771KA2 takes the source byte from the command message and makes it the destination

byte of the reply message. In our example, the reply message is sent back to the 1770KF2, node address

012 octal (0A hex).

SRC (source) 09 Indicates the Data Highway node address that is the source of the message. In this example, the reply is

being sent from the 1771KA2 at node address 011 octal (09 hex).

CMD (command) 41 Indicates the specific type of command. In a reply packet, 40 hex is added to the CMD byte to indicate that

the packet is a reply. In this example, the CMD byte in the command message was 01 hex (unprotected

read), so the CMD byte in the reply message is 41 hex.

STS (status) 00 Indicates the status of the message. If there is a problem with the message or the network, a status code

appears in this byte. In our example, the message is successful (status code 00 hex). (For a list of status

codes, see Chapter 8, Message Packet Status Codes (STS, EXT STS).")

TNS (transaction)

(2 bytes)

01 00 Indicates a specific transaction value for each message. The TNS value for the reply message is the same

as the TNS value for the command message. This allows the computer to keep track of commands and their

associated replies.

DATA FF FF In our example, the computer reads two actual bytes of data from the PLC2/30 data table (octal word 011).

These bytes of data are FF FF hex (1111 1111 1111 1111 binary). This indicates that all 16 bits at octal word

011 are set on.

DLE ETX (2

bytes)

10 03 Indicates the termination of the reply message.

BCC (block check

character)

AD Used to check the accuracy of the message transmission. You can optionally use CRC bytes here.

The BCC value must equal the 2's compliment of the 8bit sum of all data bytes between DLE STX and DLE

ETX. (For more information on BCC and CRC error checking, see page 5-4.)

DLE ACK 10 06 Sent from the computer back to the module (1770KF2) to indicate that the computer successfully received

the message. If the BCC value calculated by the module does not match the BCC value in the message

packet, the module sends a DLE NAK (10 15 hex) instead of the DLE ACK (hex). If the module does not

receive a DLE ACK or DLE NAK from the computer within approximately one second (1771KE, KF, KG

only), it sends a DLE ENQ to see if retransmission is necessary.

1 2 ... 232 233 234 235 236 237 238 239 240 241 242 ... 250 251

Brak uwag

Rockwell-automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command Instrukcja Użytkownika Strona 237