UM1518 datasheet(25/37 Pages) STMICROELECTRONICS

25 / 37 page

UM1518

Services

Doc ID 022791 Rev 2

25/37

Figure 23.

Payload subfields on DL frames of Ping session

The Master sends periodically, with an inter-packet time selected by the user (in seconds), a

burst of DL frames built (see Figure 23) with a fixed value on Slave Address subfields (1

byte) and an increment value on Frame number subfield. The Frame number value is

managed by the GUI and it is equal to 0 on the first DL frame of the Ping session, it

increases on next sent frames up to value 255 hexadecimal FF. The next frame, after that

with a number of frames equal to 255, is built with a subfield equal to 0.

The user chooses the number of frames to be transmitted by the Master during the Ping

session, which ends after sending this number of frames.

After each sent frame, a further frame is expected to be received to successfully accomplish

a single Ping loopback, within an interval with length equal to inter-packet time. In case of a

frame received by the Master node, the GUI compares the electrical parameters and

Payload to those for transmitted frame. Three cases are taken into account by the GUI:

1. A DL_DataIndication has been notified by the modem reporting the same electrical

features (modulation, carrier frequency), the Payload length and data values (over the three

subfields) as the last ones to be transmitted. The single Ping loopback is reported as

successful by increasing a dedicated "Ping OK" counter;

2. A DL_DataIndication has been notified by the modem reporting different electrical

features or Payload data. As DL_DataIndication assumes a correct check on CRC of the

powerline frames, the communication link from Slave to Master is considered as good, while

the difference of frames are supposed to be due to the link from Master to Slave. Hence, the

single Ping loopback is reported as failed, by increasing a dedicated "Ping Wrong Link 1"

counter;

3. A DL_SnifferIndication has been notified by the modem. The communication link from

Slave to Master is judged to be the cause of the wrong single Ping loopback and dedicated

"Ping Wrong Link 2" counter increases.

In case of no Indication message notified by the ST7580 within the inter-packet time interval,

the single Ping loopback is judged as failed, by increasing the corresponding "Ping Not OK"

counter.

Figure 24 reports the flowchart of Master node throughout Ping session:

DL SDU

Payload

from 0 up to246 bytes

PHY SDU

1 byte

CRC

4 byte, LE

1 byte

from 0 to 244 bytes

AM16522v1

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