Using the Ethernet Port

Description, Continued

Words 24, 25 Increments whenever a client attempts to connect to the M1 Ethernet, and fails,

Receive Buffer because there is no available server path. The M1 Ethernet supports 14

Errorssimultaneous data paths and 2 program paths before this counter can increment. This error indicates poor application architecture.

Transmission Errors

Words 26, 27

Increments when the M1 is unable to transmit an Ethernet response frame because

Transmit Buffer

all frame buffers are in use. For example, the M1 has 16 PING reply buffers. If all

Errors

16 PING buffers contain PING replies, ready to be transmitted, but this station’s

 

transmission is delayed because of collisions and backoff, and one more PING

 

request is received, then the new PING request is discarded and the counter is

 

incremented. This error can occur for PING, ARP, and connection attempt to server

 

path. Although this error is theoretically possible, it is not usually encountered.

Words 28, 29 Silo This field counts M1 TCP/IP retries. All M1 clients and server use the TCP/IP

Underflowprotocol which implements sequence numbers and timeouts. Whenever TCP/IP data is pushed from the M1, a subsequent acknowledgement of receipt of M1 data must be received within the timeout period, or else the M1 issues a retry. Retries may be the result of any of the following conditions:

λThe original M1 data frame was garbled, corrupted, and lost

λThe target TCP/IP stack is operating more slowly than the M1 retry rate For Modbus 502 servers, the M1 initiates retries after (1, 1, 2, 2, 4, 8) seconds.

For Modbus 502 clients, the M1 retry rate is the larger of:

λ1/4 the health timeout for Ethernet I/O Scanner data (see Accessing the Ethernet / I/O Scanner Screen on page 345, OR:

λ4 times the previous measured TCP/IP round trip time for i/o Scanner MSTR block.

Continued on next page

870 USE 101 10 V..2

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Schneider Electric Processor Adapter manual Words 26, Transmit Buffer, Errors