Modbus Protocol Specification
(0C Hex) Fetch Comm Event Log
tải về 0.61 Mb. Chế độ xem pdf
|
| 2.2.9 12 (0C Hex) Fetch Comm Event Log
Returns a status word, event count, message count, and a field of event bytes from the slave. Broadcast is not supported. The status word and event count are identical to that returned by the Fetch Communications Event Counter function (11, 0B hex). The message counter contains the quantity of messages processed by the slave since its last restart, clear counters operation, or power-up. This count is identical to that returned by the Diagnostic function (code 08), subfunction Return Bus Message Count (code 11, 0B hex). The event bytes field contains 0 ... 64 bytes, with each byte corresponding to the status of one Modbus send or receive operation for the slave. The events are entered by the slave into the field in chronological order. Byte 0 is the most recent event. Each new byte flushes the oldest byte from the field. Query Here is an example of a request to fetch the communications event log in slave device 17: http://www.modicon.com/techpubs/dcon7.html (14 of 36) [1/11/2000 10:41:04 PM] Response The normal response contains a two-byte status word field, a two-byte event count field, a two-byte message count field, and a field containing 0 ... 64 bytes of events. A byte-count field defines the total length of the data in these four fields. Here is an example of a response to the query: In this example, the status word is 00 00 hex, indicating that the slave is not processing a program function. The event count shows that 264 (01 08 hex) events have been counted by the slave. The message count shows that 289 (01 21 hex) messages have been processed. The most recent communications event is shown in the Event 0 byte. Its contents (20 hex) show that the slave has most recently entered the Listen Only Mode. The previous event is shown in the Event 1 byte. Its contents (00 hex) show that the slave received a Communications Restart. tải về 0.61 Mb. Chia sẻ với bạn bè của bạn:
|